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Solar-Terrestrial
Predictions
Proceedings
Volume 4: Prediction of Terrestrial Effects
of Solar Activity
Richard F. Donnelly, Editor
Space Environment Laboratory
Boulder, Colorado
•%r£S O* K
U.S. DEPARTMENT OF COMMERCE
•National Oceanic and Atmospheric Administration
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SOLAR-TERRESTRIAL PREDICTIONS PROCEEDINGS
VOLUME IV
PREDICTION OF TERRESTRIAL EFFECTS OF SOLAR ACTIVITY
Edited by
Richard F. -Donnel ly
Space Environment Laboratory
Boulder, Colorado 80303, U.S.A.
March 1980
The International Solar-Terrestrial Predictions Proceedings and Work-
shop Program was hosted by the NOAA Space Environment Laboratory. The
workshop was held April 23~27 , 1979, at the College Inn in Boulder, Colorado,
Science co-sponsors of the program:
AGU: American Geophysical Union
AMS : American Meteorological Society
COSPAR: Committee on Space Research
IAGA: International Association of Geomagnetism and Aeronomy
IAU: International Astronomical Union
IUWDS: International URSIGRAM and World Days Service
SCOSTEP: Scientific Committee on Solar-Terrestrial Physics
URSI: Union Radio Scientifique Internationale; Commissions E and G
Science and financial co-sponsors of the program:
Air Force Geophysics Laboratory
Air Force Office of Scientific Research
Department of Energy
National Aeronautics and Space Administration
National Science Foundation
NOAA Environmental Research Laboratories
NOTICE
The papers in this volume express the opinions and suggestions of the
authors. They are presented here in the spirit of encouraging further study,
testing and development of solar-terrestrial predictions. The presentation of
the papers in this volume does not constitute endorsement or approval by the
Environmental Research Laboratories or by the cosponsors of the International
Solar-Terrestrial Predictions Proceedings and Workshop Program.
The Environmental Research Laboratories do not approve, recommend, or
endorse any proprietary product or proprietary material mentioned in this
publication. No reference shall be made to the Environmental Research
Laboratories or to this publication furnished by the Environmental Research
Laboratories in any advertising or sales promotion which would indicate or
imply that the Environmental Research Laboratories approve, recommend, or
endorse any proprietary product or proprietary material mentioned herein,
or which has as its purpose an intent to cause directly or indirectly the
advertised product to be used or purchased because of this Environmental
Research Laboratories publication.
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
(Order by SD Stock No. 003-017-00479-1)
11
PREFACE
The International Solar-Terrestrial Prediction Proceedings and Workshop Pro-
gram (ISTP/P-W Program) included the following: (1) an open call for contrib-
uted papers on solar-terrestrial predictions; (2) invited review papers about
(a) the prediction, warning and monitoring services of groups that regularly
issue solar-terrestrial predictions; (b) the current and future needs for
predictions by groups that use solar-terrestrial predictions, and (c) current
knowledge of selected topics in solar-terrestrial physics and applications;
(3) working groups on fourteen areas of interest for solar-terrestrial pre-
dictions; (k) a preprint exchange from October, 1978 through March, 1979;
(5) a workshop of representatives of the working groups; and (6) the Solar-
Terrestrial Predictions Proceedings. These proceedings consist of four volumes
U.S. Government Printing Office,
Superintendent of Documents Stock No.
Volume I. Prediction Group Reports (003-023-000^1-9)
Volume II. Working Group Reports and Reviews (003-017-00^71-6)
Volume III. Solar Activity Predictions (003-01 7-00^73-2)
Volume IV. Predict ions of Terrestrial Effects of Solar Activity
Volume I reviews the current practice in solar-terrestrial predictions. Vol-
ume II presents the recommendations and reports developed by the working
groups at the workshop. Topical reviews and papers on the current and future
needs for predictions are also included. The program did not include a con-
ference where the authors presented their papers orally. Working group par-
ticipants were asked to read the preprints and correspond with the authors
and other group members before meeting at the workshop. Participants in-
cluded forecasters, scientists and prediction users. Volumes III and IV pre-
sent individual suggestions for particular prediction schemes.
The goals of the program were as follows: (1) to determine and document the
current state-of-the-art of solar-terrestrial predictions, the applications of
these predictions, and the future needs for solar-terrestrial predictions,
(2) to encourage research, development and evaluation of solar-terrestrial
predictions, and (3) to provide indepth interaction of prediction users, fore-
casters and scientists involved in the research and development of prediction
techniques. To achieve the first goal, we invited forecast groups and user
groups to review their activities. The working groups concentrated on deriv-
ing recommendations for future needs pertinent to solar-terrestrial predic-
tions. The early call for contributed papers was made to achieve the second
goal, i.e. authors had more than a year to orient their work towards a paper
on predictions. The workshop was aimed at the third goal
Ri chard F. Donnel ly
N0AA/ERL/SEL
Boulder, Colorado 80303 USA
March 21 , 1980
i i i
OVERVIEW
Volumes Ml and IV include papers contributed in response to an open call
for papers about solar- terrest r i a 1 predictions. Whereas Volume III involves
solar activity predictions, Volume IV involves the prediction of the terres-
trial effects of solar activity. Chapter A includes papers about geomagnetic
activity predictions ranging from solar cycle variations, solar rotation var-
iations to the disturbances following sudden commencements or sudden impulses.
The use of interplanetary data to predict geomagnetic activity is discussed
in several papers and is currently a very active topic in research and develop-
ment of geomagnetic predictions. Geomagnetic activity can be set off both by
solar flare disturbances and the interplanetary magnetic field sector structure
passages. During the declining phase of a solar cycle, long lasting coronal
holes can cause recurrent geomagnetic activity related to the solar rotation
rate. Studies of geomagnetic activity have had a marked influence on studies
of the solar cycle by emphasizing the strong role of long lasting solar
structure (recurring over several solar rotations) during the decay of a solar
cycle.
Chapter B includes papers about predicting energetic magnetospher i c
particles. Predictions of substorm-rel ated particles, ring current develop-
ment and electron precipitation into the Earth's atmosphere are discussed.
Volume IV includes many papers about predicting ionospheric and radio
propagation conditions, which reflects the continued importance of this
traditional applications area of solar-terrestrial predictions. Physicists
tend to assume that the way to predict the ionospheric and radio propagation
effects of solar activity is to try to predict the solar activity and then
estimate the interplanetary, magnetospher i c , geomagnetic and then the ion-
ospheric and radio propagation effects. However, many of these papers for
radio propagation predictions are based primarily on empirical or statistical
relations. Predictions of sporadic E, spread F, and scintillations generally
involve statistical or empirical predictions and still seem quite far removed
from the phys i cal -pred i ct ion approach.
Chapter C includes ionospheric predictions, including storm effects,
sporadic E, solar-flare induced sudden ionospheric disturbances, and high
latitude particle precipitation induced disturbances. Chapter D includes
radio propagation predictions. Predictions for trans ionospheric propagation
is a relatively new and growing area within radio propagation predictions.
Chapter E includes satellite drag applications and geomagnetic activity
effects on long-line electric power systems at high latitudes. Chapter F
involves climate predictions involving solar activity. The papers in Chapters
E and F supplement the papers on these topics in Volume II.
In recent years, statistical studies of the correlation between solar
activity and climate finally raised that subject to a level of respectability
so that research is now being conducted to try to systematically determine
the physical processes involved. However, it still is a controversial subject
area. The arguments against such correlative subjects, where the physical
processes involved are not clear, tend to initially involve questions of
whether the correlations are statistically significant. Such subjects tend
i v
to involve several fields of science where the experts in each of the fields
are naturally skeptical of papers that link their area of expertise with
another distant subject area with which they are unfamiliar. Editors find it
difficult to obtain competent overall reviews. In the reviews of papers on
the relation between solar activity and climate, one group of participants
systematically recommended that the papers be accepted with little or no need
for revisions. A second group systematically recommended that the same papers
be rejected outright without considering further revisions. In other words,
there was a marked polarization among the participants. Fortunately the work-
shop activities in this area were peaceful and constructive.
Chapter G includes some controversial
between solar-activity and terrestrial sei
relation between solar activity and biolog
correlating human behavior or biological e
scattered through the literature in the pa
ignored by the mainstream of science or cr
istical significance. Seldom is the criti
logical scientific way. Perhaps both the
solar activity are modulated by the same u
ulation doesn't count for much in science
editor, do not place much significance on
supposed to be statistically significant u
possible physical link exists. Controvers
point out these topics of research within
predictions and to encourage further resea
criticism of these topics.
topics, namely the correlation
smic activity and the possible
ical effects. Numerous papers
ffects with solar activity exist
st three decades. These are mainly
iticized as appearing to lack stat-
cism published and presented in a
variations in seismic activity and
nknown galactic force. Such spec-
Many physicists, including this
correlative studies even if they are
nless a reasonable explanation of a
ial papers have been included to
the broad field of solar-terrestrial
rch and constructive scientific
Most of the papers in these proceedings were reviewed by participants
in the Solar-Terrestrial Predictions Proceedings and Workshop Program, where
the reviews were used to try to improve the papers. About a dozen papers
were rejected. Almost all papers required revisions. In some cases, we have
tried to improve the English presentation of the paper and hope that the
meaning intended by the author has not beej? acci dental 1 y d i storted
Richard F«. Donnelly, March 20, 1 980
I STP/P-W Program Chairman
ACKNOWLEDGEMENTS
The editor wishes to thank the many persons who helped conduct the work-
shop or produce and distribute the proceedings. I appreciate the professional
help of Larry Christiansen and his staff of the University of Colorado Center
for Conferences and Management and the staff of the College Inn for their help
in conducting the workshop. I am grateful to Sandy Rush, Lindsay Murdock and
Dorothy Burdick for their help in editing these proceedings and preparing them
for the printer. I wish to thank Judy Jasan for her typing and David Klock and
Linda Kishimoto for help in distributing the proceedings to the workshop parti-
cipants. I thank Steve Suess for his help on the Editorial Review Committee.
Digitized by the Internet Archive
in 2012 with funding from
LYRASIS Members and Sloan Foundation
http://archive.org/details/solarterrestrOOinte
SOLAR TERRESTRIAL PREDICTIONS PROCEEDINGS
VOLUME IV PREDICTION OF THE TERRESTRIAL-EFFECTS OF SOLAR ACTIVITY
TABLE OF CONTENTS
Page
Preface i i i
Overview iv
Acknowledgements v
A. GEOMAGNETIC ACTIVITY PREDICTIONS
Prediction of Geomagnetic Activities From Solar Wind Parameters
Based on the Linear Prediction Theory — T. lyemori and H. Maeda A - 1
The 21st Solar Cycle: aa Index of Geomagnetic Activity —
J . Feynman A - 8
Computer Forecasting of Geomagnetic Disturbances —
T.V. Ga i voronskaya and V.P. Kuleshova A - 19
Interplanetary Magnetic Field and Polar Cap Magnetic Disturbances:
Using the Data for Prediction of Auroral Electrojet Activity —
O.A. Troshichev, N.P. Dmitrieva, B.M. Kuznetsov, and V.P. Vasiliev...A - 2k
Short-Term Forecasting of Geomagnetic Storms Associated With High-
Speed Solar Wind Streams — V.M. Mishin, V.V. Shelomentsev,
A.D. Bazarzhapov, and L.P. Sergeeva A - 37
Solar Cycle Effect of 27_Day Recurrent Geomagnetic Storm —
T. Ondoh and Y. Nakamura A - k(>
Short-Term Predictions of a Sudden Geomagnetic Impulse Value on
the Basis of the Interplanetary Data — S.A. Grib A - 53
Prediction of Substorm Activities — T. Saito A - 61
Short-Term Forecasting of the Substorm Breakup Phase Based on Ground
Magnetic Observations in the Zone of Magnetospher i c Cleft Projection —
V.V. Shelomentsev, V.M. Mishin and T.I. Saifudinova A - 69
Development of Disturbances After SC and SI — I.N. Men'shutina A - 80
Working Group Report on Geomagnetic Storms - S.I. Akasofu A - 91
Addendum: Workshop Report on Geomagnetic Disturbance Predictions -
J. A. Joselyn A - 115
B. MAGNETOSPHERIC PARTICLE PREDICTIONS
Prediction of High-Energy (>0.3 MeV) Substorm-Related Magnetospher ic
Particles - D.N. Baker, R.D. Belian, P.R. Higbie, and E.W. Hones,
Jr B- 1
vii
The Use of > 30 keV Electron Anisotropics At 6.6 R to Predict Mag-
netospheric Substorms - D. N. Baker, P.R. Higbie, E.W. Hones, Jr.,
and R. D. Bel i an _ B _ ^2
Evolution of Substorm and Quiet -Time Electron Anisotropies
(3° 1 Ee 1 30° keV) at 6'6 RE ~ P'R- H'9b'e, D.N. Baker, R.D. Belian
and E. W. Hones , Jr g _ 23
Predicting Partial Ring Current Development -C.R. Clauer and
R.L. McPherron .B - kh
On the Predictability of Radiation Belt Electron Precipitation Into
the Earth's Atmosphere Following Magnetic Storms -W.N. Spjeldvik,
and L. R. Lyons . B - 59
C. IONOSPHERIC PREDICTIONS
Geomagnetic Activity Control of Ionospheric Variability — M. Mendillo,
F.X. Lynch, and J. A. Klobuchar C - 1
A Morphology-Based Prediction Scheme for the Coupled Latitudinal and
Local-Time Development of F-Region Storms — M. Mendillo and J. A.
Klobuchar C - 15
On the Possibility to Predict Variations in the F2-Region Parameters
as a Function of the IMF Direction — R.A. Zevakina and E.V. Lavrova..C - 27
Forecasting of 6foF2-Var iat ions for Ionospheric Disturbances — V.P.
Kuleshova, E.V. Lavrova and L.N. Lyakhova C - 37
Fundamentals of the Physical Forecast of Ionospheric Plasma —M.N.
Vlasov C - 41
Self-Consistent Model of the Ionospheric Plasma and the Hydrodynamic
Forecast - M.N. Vlasov and A.G. Kolesnik C - kl
Prediction of the Parameters of the Maximum of the Vertical Electron
Density Gradient — T.A. Anufrieva, T.L. Gulyaeva, G.F. Kadukhin,
T.N. Soboleva, and A.G. Shi ionsky C - 57
Model Calculations of Electric Fields and Currents in the High-Latitude
E Region for Predictions of Ionospheric Variations — S. Matsushita
and Y. Kami de C - 65
Statistical Prediction of E -Layer Parameters and Echo-Signal
Characteristics - T.S. Kerblay and G.S. Nosova C - 77
Forecast of Critical Frequency and Height of Maximum Density of Mid-
Latitude E-Layer — G.S. I vanov-Kholodny and A. A. Nusinov C - 82
Daytime Sporadic-E Blanketing Frequency Prediction — A.E. Giraldez...C - 87
vm
Short Term Prediction of Ionospheric Disturbances — S.N. Mitra and
M. Sain C- 107
The Inference of Severe Night-Time Disturbances of the D Region From
High-Latitude Riometer Observations — J.K. Hargreaves C - 110
The Possible Prediction of SID's Using the Slowly Varying Component
of the Solar Radio Flux at 3.2 CM - Z.Y. Zhu, A.H. Zhou and
S.R. Zhou C - 11 *»
D. RADIO PROPAGATION PREDICTIONS
1. Trans ionospheric Propagation Predictions
An Improved Ionospheric Irregularity Model — D.G. Singleton Dl - 1
Predicting Trans ionospher i c Propagation Conditions —D.G. Singleton. . Dl - 16
Model of Phase and Amplitude Scintillations From In-Situ Measurements —
S. Basu and S. Basu Dl - 32
A Resume of Anticipated Fleetsatcom and Gapfiller Scintillation Effects
During the Peak of Solar Cycle 21 (1 980-1 982) - J.M. Goodman Dl - 50
Ionospheric Refractive Correction Using an Adaptive Procedure —
D.E. Donatelli and R.S. Allen Dl - 65
Prediction of Trans ionospheric Signal Time Delays at Widely Separate
Locations Using Correlative Techniques — H. Soicher Dl - 81
2. HF Ionosphere-Reflected Propagation Predictions
HF Communications Predictions 1978 (An Economical Up-To-Date Computer
Code, AMBCOM) -V.E. Hatfield D2 - 1
The Statistical Properties of the Disturbed High-Latitude Ionosphere
in Radio Wave Propagation Computations — E.M. Kovalevskaya and E.M.
Zhul ina D2 - 16
Prediction of HF Communication Disturbances by Pre-SC HF Field
Increases on Polar Paths Crossing the Auroral Zone — T. Ondoh and
K. Obu D2 - 21
Minicomputer Simulation of Ionospheric Radiowave Propagation at
Decametric Wavelengths — D.D. Meisel, B. Duke and W.D. Savedoff D2 - 31
A Simplified Computer Method For Long-Term Calculation of HF Sky-Wave
Circuits — A.A.E. Picquenard and E. Rodr iques de Paula D2 - k]
Prediction of foF2 by the Monthly Ratio (MR) Method - P.S. N. Murthy
C.S.R. Rao, and M. Sain D2 - 5**
IX
HF Communication Problems at Low Latitudes Due to Steep Spatial and
Temporal Gradients — D.R. Lakshmi , S. Aggarwal , P.K. Pasricha and
B.M. Reddy D2 - 58
Prediction of the Characteristics of a Radio Signal Reflected from
Horizontal ly- Inhomogeneous Ionosphere and the Relevant Requirements
for Prediction of Ionospheric Parameters — T.S. Kerblay, E.M.
Kovalevskaya, E.M. Zhulina and L.M. Ishkova D2 - 65
Using Solar Flux Index Predictions to Forecast HF Radio Wave Propa-
gation - D.J. Snyder D2 - Ik
Graf ex Predictions — J. F. Turner D2 - 85
3. Absorption, Field Strength and Radio Noise Predictions
Prediction of Radio Wave Absorption in the Ionosphere — J.O.
Oy inloye D3 - 1
On the Short-Term Prediction of the Space-Time Distribution of Auroral
Absorption — R.A. Zevakina and M.V. Kiseleva D3 - 1 *»
Determination of the Solar Cycle Variation of HF Radio Wave Absorption
at Low Latitude - K.M. Kotadia, A Gupta and R.M. Kotak D3 - 20
Prediction of Riometer Absorption from Solar Flare Radio Burst
Characteristics — P. Bakshi and W.R. Barron D3 - 26
A Method of Predicting Skywave Field Strength in HF Bands in Tropical
Zones - O.P. Sehgal and H.O. Agrawal D3 - 31
Unpredicted Variations in D-Region Response to Solar X-Ray Events —
R.H. Doherty D3 - 35
Secular Variation of Occurrence Rate and Dispersion of Low-Latitude
Whistlers During the Solar Cycle Nos. 19 and 20 — Y. Tanaka, M.
Hayakawa, J. Ohtsu and A. Iwai ■ D3 - ^8
Atmospheric Radio Noise Measurements in LF/MF Bands — A.K.
Bhatnagar and M. Sain D3 - 55
Prediction of Waveguide Propagation of Radio Waves Using the Extremal-
Parametric Method Based on Predicted Ionospheric Parameters —
A.G. Shlionsky D3 - 60
:. SATELLITE AND ELECTRIC POWER APPLICATIONS
Anamalous Satellite Drag and the Green-Line Corona — R.C. Altrock....E - 1
Effects of Magnetospheri c Disturbances on the Geoelectric Field in Auroral
and Sub-Auroral Regions, and Interactions With HV-DC/AC Electric Power
Lines: Large-scale man-made effects on the global aeronmic environment —
W.M. Boerner, J.B. Cole and W.R. Goddard E - 5
F. SUN ■* WEATHER PREDICTIONS
The Solar Predict ion of Climatic Changes — H.C. Willett F - 1
Weather and Climate Predictions in the Northern Hemisphere Based on
Solar- Terrestrial Re 1 at ions — V. Bucha F - 18
The Effects of Changing the Solar Constant on the General Circulation
of the Earth's Atmosphere — T. Asakura and Y. Tanaka F - kk
Meteorological Microseisms and Sun-Weather Relationships —
J . Lastovicka F - 5^
On the Variation of the Annual Mean Sea - Level Pressure in Latitude
Zones of the Northern Hemisphere —J. Xanthakis, B. Tritakis and
B. Petropoulos F - 63
The 1 3- 6- Day Oscillation in the Stratosphere — A. Ebel F - 77
A Consideration of the Possible Use For Weather Forecasting of a
Particular Sun-Weather Relation — R.G. Williams and M.J. Rycroft F - 85
G. MISCELLANEOUS PREDICTIONS
A Prediction of the Influence of T, [NO] and q(0„) on the Positive
Ion Composition at the Mesopause Region — D.K. Cnakrabarty and
P. Chakrabarty G - 1
On Predicting the Parameters of Medium Scale Gravity Waves With the
Onset of Tropospheric Jet Stream — O.P. Nag pal G - 8
Solar Relationship and Prediction of Seismic Activity of the Earth —
Y.D. Kalinin, and V.M. Kiselev G - 23
Solar Terrestrial Prediction - Aspects for Preventive Medicine —
E. Stoupel G - 29
XI
A. GEOMAGNETIC ACTIVITY PREDICTIONS
PREDICTION OF GEOMAGNETIC ACTIVITIES FROM SOLAR WIND PARAMETERS
BASED ON THE LINEAR PREDICTION THEORY
Toshihiko lyemori and Hiroshi Maeda
Geophysical Institute, Kyoto University,
Kyoto 606, Japan
Geomagnetic activity described by the Dst, AL and AU indices is
predicted from solar wind parameters (i.e. interplanetary magnetic
field southward component Bz(<0), wind velocity V, and particle
density N) . The hourly value data are used. The prediction tech-
nique is based on the Wiener's linear prediction theory. That is,
first we calculate the impulse response function of one of the
geomagnetic indices to the interplanetary electric field, -V«Bz,
from both the index and the solar wind parameters, and then we
predict the geomagnetic index using the impulse response function
thus calculated and the data of the solar wind parameters. It is
emphasized that the impulse response functions of the indices
differ from each other and the effect of the interplanetary elec-
tric field, -V'Bz, lasts for more than several hours.
1. INTRODUCTION
Since the close relationship between the geomagnetic activity and the
north-to-south component of the interplanetary magnetic field (IMF-Bz) was
recognized, several attempts to get a quantitative relationship between them
have been made. For example, Arnoldy(1971) showed the linear relationship
between the auroral electrojet activity index AE and the IMF southward compo-
nent (Bz<0), and predicted the AE index from the solar wind data for two hours
before the prediction time. Burton et al.(1975) showed empirically a simple
relationship between the Dst index and the interplanetary electric field
dawn-to-dusk component, -V-Bz, where V denotes the solar wind bulk velocity,
and predicted the Dst index from the solar wind data preceding twenty-five
minutes.
In this paper, we try to predict these geomagnetic indices, AL, AU and Dst,
from the solar wind data by somewhat different method. That is, by the method
based on the Wiener's linear prediction theory. The AL and AU indices are
regarded as a measure of the intensity of the westward and the eastward
auroral electrojet, respectively. The Dst index is mainly a measure of the
A - 1
ring current intensity, but the intensity of the solar wind pressure and that
of the magnetopause current also contribute to the Dst index (Davis and
Sugiura, 1966) .
2. PREDICTION TECHNIQUE
We assume that the magnetosphere acts as a linear system to the interplane-
tary electric field dawn-to-dusk component, -V«Bz, and causes the geomagnetic
disturbances. That is, we consider a linear system with constant coefficients,
the input of it is -V'Bz and the output is one of the geomagnetic indices, AL,
AU or Dst.
If we have sufficient knowledge of the system, we will be able to predict
the output of the system from the input data. In the case of a linear system
with constant coefficients, the property of the system can be completely ex-
pressed by the impulse response function h(x), and the output data w(t) , where
't' denotes the time and is connected with the input data f(t) through eq.(l).
W(t) = h(T)f(t-T)dT (1)
J 0
The function h(i) can be calculated from w(t) and f(t) by the method of
root-mean-square (RMS) error criterion by Wiener (1949) and the algorithm of
calculation for the discrete time series was given by Levinson(1949) in
Wiener' s book.
In our case, the input f(t) is the interplanetary electric field, -V'Bz,
where we put Bz equal to zero when Bz is positive(i.e. northward), the output
w(t) is one of the geomagnetic indices, Dst, AL or AU, and the impulse resp-
onse function h(x) is calculated for each index (Iyemori et al.,1978).
CALCULATION AND CHARACTER OF h(x)
All the data used in this study are hourly values and the periods that the
data cover are listed in Table 1, the total being 250 days. These non-contin-
uous periods are connected next to each other and regarded as one continuous
time series having the length of 250 days. The interplanetary data used are ;
(a) IMF data book(king, 1975) and (b) the composite interplanetary plasma data
tape, both of which were supplied from WDC-A for Solar Terrestrial Physics.
The IMF data are used in a geocentric solar-magnetospheric coordinate system
(GSM) (Russell, 1971) . The geomagnetic indices used are ; (c) Dst index by
Sugiura and Poros(1971) and (d) AE(AL and AU) index by Allen et al . (1973, 1974).
Figure 1 shows the impulse response function thus calculated for Dst°, AL
and AU, where the Dst° is defined by eq.(2) to remove the effect of compres-
sion of the magnetosphere caused by the kinetic pressure change of the solar
wind (Burton et al.,1975).
Dst° = Dst - aVNV1 + b (2)
Here N is the number density (particles/cm3) of the solar wind, V is the bulk
velocity (km/sec), 'a' and 'b' are constants, and we used the numerical values
0.0255 and 20.6 for 'a' and 'b' respectively. The symbol 'M' and 'EM' in
Figure 1 indicate the length of the impulse response function which is calcu-
lated and the efficiency as a predictor. That is, if EM is nearly equal to
unity, it shows that the output data (e.g. geomagnetic indices) is almost
completely predicted by the impulse response function from the input data (e.g.
interplanetary parameters), and if EM is nearly zero, the output data is little
predicted (Levinson,1949) .
The response function of Dst°(top panel in Figure 1) is roughly consistent
with what is expected from the result of Burton et al.(1975), but our result
shows a more complex feature of the response. That is, after the main devel-
opment appearing in about one hour, there exist a second development with a
time lag of about five hours. Similar second developments are seen in the
response function of AL index (middle panel in Figure 1) and, though slight,
in that of AU index. These are indicated by arrows in Figure 1. This result
means that the effect of the interplanetary electric field lasts for more than
several hours for the development of geomagnetic disturbances (cf. Arnoldy,
1971).
The other point of emphasis is the difference between the response functions
of AL index and that of AU index. This means that the mechanism of development
of the westward auroral electro jet, a measure of it is AL index, is different
from that of the eastward auroral electrojet (AU index) (Iyemori et al.,1978).
TABLE 1. Periods and each
time span that the data
cover.
PERIOD
SPAN
(month/day/ year)
(day)
1/19/67 -
1/31/67
13
2/ 3/67 -
2/13/67
11
2/16/67 -
2/27/67
12
3/ 3/67 -
3/13/67
11
7/25/67 -
8/ 9/67
16
8/24/67 -
9/17/67
25
9/24/67 -
10/13/67
20
10/16/67 -
11/20/67
36
11/23/67 -
12/10/67
18
12/21/67 -
1/ 9/68
20
1/23/68 -
2/ 1/68
10
2/ 5/68 -
2/19/68
15
2/23/68 -
3/ 9/68
16
3/13/68 -
3/26/68
14
3/30/68 -
4/11/68
13
TOTAL
250
'10
TIME LAG ( hour)
Fig.l Impulse response functions for
geomagnetic indices, Dst, AL, and AU.
The input data for the system is inter-
planetary electric field, -V-Bz, where
we put Bz equal to zero when Bz is posi
tive. The data used have the length of
250 days.
A - 3
EXAMPLE
Figure 3 to 5 show some examples of prediction. The solid lines denote
the data of the solar wind (number density N, bulk velocity V, and IMF-Z com-
ponent Bz in GSM coordinate system) and the geomagnetic indices (AU, AL, and
Dst) . The broken lines denote the predicted values for each index calculated
by the impulse response function in Figure 1 using the solar wind parameters
covering from forty hours before up to the time when the index is predicted.
This time span (40 hours) of the impulse response function for prediction is
long enough, because the value of EM (i.e. the efficiency of prediction) in
Figure 2 are nearly saturated before 40 hours (M=40) . Each figure (Figure 3
to 5) covers the time span of ten days and the number above the base line of
the Dst index denotes the number of days counted from the first of January.
Figure 3 covers the period from February 26 to March 6 in 1968, when the
geomagnetic activities are moderately high. The predicted values of AL and
Dst index coincide with the observed values fairly well, but those of AU index
do not coincide so well. Figure 4 covers the period from October 18 to October
27 in 1967, when the geomagnetic activities are comparatively quiet.
Figure 5 covers the period from November 29 to December 8 in 1967, when the
geomagnetic activities are moderately high similar, to the period in Figure 3.
But in this case, the velocity of the solar wind, V, is rather high after the
day 339 when the predicted values are much smaller than the observed values
for all indices. The tendency for the predicted values from interplanetary
electric field, -V-Bz, to be smaller than the observed values when the solar
wind velocity is high (i.e. more than 500 km/sec) is rather commonly seen.
The difference between the predicted and the observed values during such a
high velocity period can be reduced to some extent if V2 • Bs is used as the
input (Murayama and Hakamada, 1975; Maezawa, 1978) ; here, Bs denotes the hourly
mean of the southward component alone, and differs from Bz when the variance
is large and Bz is around zero. However, this tendency still remains. So,
this may suggest that the solar wind energy is transferred into the magneto-
sphere not only in a form proportional to -V*Bz (or V2-Bs) but also in other
forms of the solar wind velocity V, for example, in a form of viscous-like
interaction.
Fig. 2 Relation between the
length of the impulse response
(M-hours) and the efficiency
of prediction (EM). The values
of EM are nearly saturated
before M becomes 40.
1.0
1 1 1 1 1 T 1
"
SO. 8
Dst0
<~i
S^ AL
1
o0,6
G
Q
r~f~ ""^^ au____
0.1
-' INPUT - -V-Bz
i i i i 1 i i i i 1 i i i i 1 i i i i 1 i i i i 1 i i i i 1 i i i > 1 ■ ■ t ■
10 20 50
LENGTH OF PREDICTOR (H)
9
OS
*9-
W
2
O
O
w
o
"v^i>/rWv^''v'y"
62 63 64 65
[NPUT-V»6Z
Fig. 3 Data(solid line) and predicted values(broken line). This
figure covers the period from February 26 (day 57) to March 6 (day
66) in 1968. The predicted values are calculated from the solar
wind parameters using the impulse response functions in Figure 1.
u
M
Eh
W
z
o
H
>■■'■' '■ i j&mjtf}f*r~ae*f*
!NPUT-V»EZ
Fig. 4 Data(solid line) and predicted values(broken lines). The
day 291 is October 18 and the day 300 is October 27 in 1967.
Geomagnetic activities are quiet comparatively in this period.
A
2?
3
23
-20
403
3
.%-"•'
CO
w
u
H
Q
2
(J
M -803
Eh
W
Z
o
o
w
"«• ■Afr/^V A/^Vw* fli-VW
!NPUT-V«6Z
Fig. 5 Data(solid line) and predicted values(broken line). The
day 333 is November 29 and the day 342 is December 8 in 1967.
The solar wind velocity is rather high after the day 339, when
the predicted values are smaller than the observed values.
This tendency is rather commonly seen in the other periods.
SUMMARY
We applied the Wiener's prediction theory to the prediction of geomagnetic
activities from the solar wind parameters. The result was successful in the
first approximation, and the impulse response functions brought some impor-
tant information about the mechanisms of geomagnetic disturbances. But some-
times, for example when the solar wind velocity was high, the prediction was
not so successful. This result may suggest another possibility for the mech-
anism of the transfer of the solar wind energy into the magnetosphere.
Therefore, to predict the geomagnetic disturbances more precisely by the
linear prediction theory, we should treat the magnetosphere as a multiple
input system and/or as a system with time dependent coefficients.
ACKNOWLEDGEMENTS
We wish to thank prof.Y.Inoue at Kyoto Industrial University, and Dr.T.
Araki and other members at our Institute for their useful discussions. The
interplanetary data have kindly been provided by the National Space Science
Data Center through the World Data Center -A for Rocket and Satellites, NASA,
A - 6
REFERENCES
Allen, J. H., C. C. Abston, and L. D. Morris (1974): Auroral electro jet mag-
netic activity indices AE(10) for 1967, Rep. UAG-33, World Data Center-A
for Solar-Terrestrial Physics.
Allen, J. H. , C. C. Abston, and L. D. Morris (1973): Auroral electrojet mag-
netic activity indices AE(ll) for 1968, Rep. UAG-29, World Data Center-A
for Solar-Terrestrial Physics.
Arnoldy, R. L. (1971): Signature in the interplanetary medium for substorm,
J. Geophys. Res. , 76: 5189.
Burton, R. K., R. L. McPherron, and C. T. Russell (1975): An empirical rela-
tionship between interplanetary conditions and Dst, J. Geophys. Res.,
80: 4204.
Davis, T. N., and M. Sugiura (1966): Auroral electrojet activity index AE
and its universal time variations, J. Geophys. Res. , 71: 785.
Iyemori, T., H. Maeda, and T. Kamei (1978): Impulse response of geomagnetic
indices to interplanetary magnetic field, J. Geomag. Geoelectr., 30:
to be published.
King, J. H. (1975): Interplanetary Magnetic Field Data Book, National Space
Science Data Center.
Levinson, N. (1949): The Wiener RMS (root -mean -square) error criterion in
filter design and prediction, Appendix B in N.Wiener's book (see below).
Maezawa, K. (1978) : Dependence of geomagnetic activity on solar wind parame-
ters: a statistical approach, Solar Terrestrial Environmental Res, in
Japan, 2: 103.
Murayama, T. , and K. Hakamada (1975): Effects of solar wind parameters on the
development of magnetospheric substorms, Planet. Space Sci., 23: 75.
Russell, C. T. (1971): Geophysical coordinate transformation, Cosmic Elec-
trodyn. , 2: 184.
Sugiura, M. , and D. J. Poros (1971): Hourly values of equatorial Dst for
years 1957 to 1970, Rep. X-645-71-278, Goddard Space Flight Center,
Greenbelt, Maryland.
Wiener, N. (1949): Extrapolation, interpolation, and smoothing of stationary
time series with engineering applications, Published by the Tech. Press
of the M.I.T. and John Wiley £ Sons, Inc., New York.
THE 21ST SOLAR CYCLE: aa INDEX OF GEOMAGNETIC ACTIVITY
Joan Feynman
National Science Foundation
Washington, D. C. 20418, USA
Analysis and prediction of geomagnetic activity and its re-
lation to long term variations in the interplanetary medium have
been hampered, until recently, by frequent changes of indices
used to describe geomagnetic variations. However, Mayaud has
re-examined the old geomagnetic records and produced a series of
commensurate data, the aa index, available since 1868 until the
present. Feynman and Crooker have shown that the variation of
aa consists of a long term (80 ^ 100 year) trend on which is
superposed an eleven year variation. The trend increased roughly
60% from the 1900' s to I960. The yearly average <aa> can be
considered as made up of two terms, the trend term (probably re-
lated to the "80 year cycle" in sunspots) and the 11 year solar
cycle variation. In this paper I discuss the properties of the
11 year variation and the trend from 1868 to the present. This
information is then used to attempt to estimate the yearly values
of <aa> that might be expected in cycle 21. I tentatively estimate
that the maximum <aa> will be about 27. However, I point out that
we may be entering the declining phase of the "80 year cycle" which
is expected to be marked by decades of erratic but generally de-
clining geomagnetic activity. If the "80 year cycle" is indeed
cyclic, then <aa> as small as 5 or 10 may be expected within the
next few decades.
1. INTRODUCTION
Although the relationship between the solar cycle and geomagnetic
activity is very close, there are many interesting and important differences
between the solar cycle variations of sunspot number and the solar cycle
variation of geomagnetic activity. The sunspot cycle and the geomagnetic
cycle both show the same solar cycle periodicity, but the phase of the geo-
magnetic cycle lags the sunspot cycle by 18 months (Fraser-Smi th , 1972).
Maximum geomagnetic activity typically occurs at a different period of the
solar cycle than maximum sunspot number. A second peak appears late in the
geomagnetic cycle, usually well after sunspot maximum. This activity is
made up of recurrent storms and the peak in the yearly average activity index
is frequently higher than that due to the non-recurrent activity appearing
earlier in the cycle (Newton, 1 9A8) . In addition the general level of geo-
magnetic activity rose by about 60% between 1900 and i960 (Russell, 1975).
A - 8
Feynman and Crooker (1978) have pointed out that this rising trend appears
strongly in the activity occurring at the minimum of the geomagnetic cycle
and is not directly related to the increase in sunspot number at sunspot
maximum that occurred during this same period.
In this paper I discuss patterns that have occurred in the solar cycle
variation of geomagnetic activity. These patterns are then projected to
cycle 21 to estimate the geomagnetic activity expected for that cycle. The
results are crude but are a first attempt to predict geomagnetic activity
year by year throughout a solar cycle.
1.1 Patterns of Geomagnetic Activity
At this stage of our understanding of geomagnetic activity, and its re-
lation to the solar wind, the predictions of geomagnetic activity must be
purely empirical. The best indicator of future activity is past activity.
Geomagnetic activity has been monitored since 1832 (Bartels, 1932). Auroral
activity and sunspot records extend the record well back into the 1 8th cen-
tury. Recent historical studies (c.f. Eddy, 1976) are now expanding the re-
cord into earlier times but will not be of concern to this study.
The longest term pattern of interest here that seems to exist in the
sunspot cycle and in geomagnetic activity is the 80 to 100 year cycle which
is seen in the amplitude of the sunspot cycle. Of course, since the sunspot
cycle record extends from about 1700 to the present, only three minima of the
80-100 year cycle have occurred. Since the record is so short it is not es-
tablished that those minima of the amplitude of the sunspot cycle actually
represent cyclic behavior. Thus, although from past experience there is
reason to expect that small sunspot cycles may occur circa the year 2,000,
this cannot be predicted with any confidence. In addition, even if the ampli-
tude modulation of sunspot cycles is cyclic, its period is uncertain to at
least 20 years, so that the minimum could well develop within the next de-
cades or not for almost a half century.
Geomagnetic activity exhibited a minimum in 1900 (Russell, 1975) which
may well have been related to the minimum in the amplitude of the sunspot
cycle (Feynman and Crooker, 1978). This association of minimum geomagnetic
disturbances with minima in the 80 ^ 100 year solar cycle is strengthened by
observations of auroral frequencies. Fritz (1873) noted that there were
marked minima in auroral activity in 1700, 1 760 and 1810. The two minima of
1700 and 1810 correspond to periods of minimum sunspot cycle amplitude. Since
auroral activity and geomagnetic activity are closely related, this suggests
that geomagnetic activity minima occur at times of sunspot amplitude minima.
Then the arguments that led to the expectation of a sunspot amplitude minimum
circa 2,000 lead also to a geomagnetic minimum during the same epoch.
As mentioned earlier, geomagnetic activity has been monitored since 1832.
Analysis has been hampered by the frequent changes in the index used to de-
scribe the activity. However, Mayaud (1973) has re-examined the magnetic
records from two antipodal stations and generated a commensurate set of data,
the aa index, available for the period from 1868 to the present. This data
will be used to establish further patterns of past geomagnetic activity.
A - 9
A
V
A
O
O
V
A"
o
o
V
Fig. 1 Sunspot and geo-
magnetic activity 1 900-
196^ (from Feynman and
Crooker, 1978). The top
panel gives the yearly
averaged sunspot number
<R>. The middle panel
shows the yearly averag-
ed geomagnetic index
<aa>. The straight line
is the trend and is dis-
cussed in the text. The
bottom panel shows <aa>
minus the trend.
The activity from 1 900 to i960 will be discussed in some detail. This
period is chosen because, as shown by Feynman and Crooker (1978), the solar
cycle variation of geomagnetic activity is particularly simple. Figure 1,
from their paper, shows the sunspot number and geomagnetic activity for that
period. The top panel gives the yearly average sunspot number R with its
tendency toward rising amplitudes. The second panel gives the yearly averages
of the aa values, <aa>. Feynman and Crooker divided the <aa> variation into
two parts, a long term trend and a solar cycle variation. The long term
trend was monoton ical ly increasing between. 1900 and i960 and is shown by the
straight line in the middle panel. The equation of the line is
<aa>t = 0.22 (T-1900) + 5-7 (1)
where T is the time in years. The bottom panel of Figure 1 shows the remain-
der when the values of <aa> given by (1) are subtracted from the measured
<aa>. This remainder, denoted by <aa>c ««»»n«s*- <-i-~ -1 -
variation during this sixty year period
exhibits the eleven year solar cycle
Feynman and Crooker point out that the changes in <aa>c are much the
same in each cycle. The cycle averaged <aa>c varies from 5-8 to 7-2 with a
mean of GJ\ and a root mean square deviation from the mean of O.A. A scatter
plot of the cycle averaged sunspot number and the cycle averaged <aa>c shows
no relation between the variables. The average solar cycle variation of geo-
magnetics during this period is calculated by superposing the data using years
of minimum <aa>c as zero epoch and averaging. Figure 2a shows the results
for 8 years after minimum and Figure 2b shows results for 8 years before min-
imum. The values in Figure 2a and 2b are not the same because the duration
A
10
AVERAGE
GEOMAGNETIC SOLAR CYCLE VARIATION
(1900-1960)
12
10
average
<aa;> 6
4
2
(a)
OH
ii
12
10
8
average
<aa>c 6
I I I I I I I I
2 4 6
10
(b) T
4
2
0!-u
_LL
2 4 6 8 10
Years after <aa>
mm
Years before <aa>min
Fig. 2 The average solar cycle variation of geomagnetic
activity <aa> for 1 900- 1 960 . The vertical bars
give the root mean square deviation from the mean.
of solar cycles varies by a year or two. Both a and b are necessary for pre-
diction. Note that both the rise and the decline of <aa>c is quite sharp so
the geomagnetic cycle has a much squarer shape than the sunspot cycle. The
rise after geomagnetic minimum is about seven units in two years, while the
drop to minimum is even more precipitous.
Geomagnetic activity during this period shows the 22 year double-sunspot
cycle found by Chernosky (1966). Figure 3a and b are superpositions of <aa>c
for the three even cycles \k, 16 and 18 and for the two and a half odd cycles
15, 17 and half of 19- In the even cycles the activity during the first half
of the cycle is relatively reduced and during the last half of the cycle it
is enhanced. The reverse is true for the odd cycles. Russell and McPherron
(1973) attribute this effect to the varying heliographic latitude dependence
of the interplanetary magnetic field caused by the tip of the sun's poles to
the plane of the ecliptic. Incidently, this explanation seems at first to
present a paradox since the intensity of geomagnetic activity during the re-
current part of the cycle is now being used as a predictor of sunspot number
maximum in the next cycle (Ohl , 1 968 ; Sargent, 1978). However, the modulat-
tion of the even and odd cycles is too small to effect the predictions ap-
preciably.
Returning now to study the long term trend in geomagnetic activity more
extensively, we will assume that the 5 1/2 solar cycle variations of geomag-
netic activity between 1 900 and i960 are typical of all solar cycle variations
The long term trend can be estimated crudely by subtracting the mean value
for the solar cycle variation shown in Figure 2 from the measured values of
<aa>.^ The results are given in Figure k. The general increase from 1900 to
I960 is clearly evident. The scatter of the points is a measure of the
A - 11
GEOMAGNETIC SOLAR CYCLE VARIATIONS
3 Cycles
(even: 14,16,18)
2/2 Cycles
(oddM5,17,1/2of19)
Time
Time
Years
Fig. 3 A superposition of the solar cycle variation <aa} for
even and odd numbered solar cycles separately. The late
period even cycles and early period odd cycles are more
disturbed than the early period even cycles or late
period odd cycles.
OBSERVED
TREND
<aa>
25
__ Trend
•
• •
20
• • •
• •
•/•
# . 15
•
•• •
• • •• • ...
•
•
.•• • \io
• •• •« •
••
• •
• • • • •
.. • ••
# *•
5
•
— • • •
*••
i i •:
1 1 1
' I 1 i
1 1 1 1
1860 70 80 90 1900 10 20 30 40 50 60 1970
Fig. k The trend in aa determined by subtracting the average
solar cycle variation in Figure 2 from the observed ^a^.
12
variation of the behavior from cycle to cycle. Note that in I960 there is a
precipitous drop followed by an equally sharp recovery in 197**. This is
another view of the observation reported by Gosling et al. (1977) that geo-
magnetic activity in the 20th solar cycle was unusual. Note that from this
view the first part of the cycle might be considered more atypical than the
last half.
During the period before 1900 the estimated trend is very erratic. This
is equivalent to saying that the solar cycle variation of <aa> does not al-
ways follow the pattern established between 1900 and I960. The period from
1868 to 1900 covers three solar cycles, the first of which has the highest
yearly sunspot number of any between 1800 and 1900 and the second is as low
as the small cycle beginning in 1901. If the 80-100 year cycle is really
cyclic, the period from 1868 to 1 900 is the decay period of a cycle whereas
the period from 1 900 to 1 960 was a buildup period. If we are entering another
decay period we may expect the trend in geomagnetic activity to be declining
and erratic.
There are several other patterns in geomagnetic activity that are useful
in making predictions. For example, Figure 1 shows that geomagnetic activity
<aa> averaged over a cycle more or less followed changes in the intensity of
the sunspot cycle. To quantify this relationship and extend it to cover the
entire period for which <aa> are available, Figure 5 shows the cycle average
sunspot number plotted against the cycle average <aa>. For each variable,
the cycle average is taken from minimum to minimum of that variable. Data
for the period between 1 900 and i960 is shown as circles. The crosses indi-
cate cycles earlier or later than this period. There is, of course, clearly
a relationship although there is considerable scatter in the points. The
same plot was made using the maximum sunspot number instead of the cycle
averaged values, however the scatter was increased. If the trend <aa> }s
is used instead of <aa> the scatter is about the same as shown in Figure 5-
Since recurrent geomagnetic activity is being used to predict the sunspot
number in the following cycle, the cycle averaged <aa> was also plotted
against the cycle averaged sunspot number in the next cycle. The scatter was
considerably increased. Part of the reason that Figure 5 shows a relation-
ship is the persistance of trends from cycle to cycle. This is particularly
true for the period between 1900 and i960, shown as circles. However, the
cycles which did not take place during this period seem to show the same re-
lationship as seen from the points marked as crosses.
Although a rough estimate of geomagnetic activity in cycle 21 could be
made from Figure 5, a more satisfactory process is to consider the non-recur-
rent geomagnetic activity early in the cycle separately from the late recur-
rent activity. In Figure 6 the cycle averaged sunspot number is plotted
against the average of the <aa> from the first, second and third year before
the minimum of the preceding sunspot cycle. The relationship is quite strong,
as has been pointed out by Ohl (1968) who studied the recurrent geomagnetic
activity and the maximum of the sunspot number in the next cycle. Sargent
(1978) uses the relationship discussed by Ohl, corrected by a factor propor-
tional to the sunspot number at minimum to predict that the maximum sunspot
number in cycle 21 will be about 150. That prediction will be used later in
this paper as the expected sunspot number for cycle 21.
A - 13
Cycle
averaged
<R>
100
90
80
70
SUNSPOT NUMBER vs.aa
O 1900-1954
X 1868- 1900, 1954-1977
60
X
50
0
40
X
o
30
o I
lx I
I
H 14 15 16 17 18 19 20 21 22 23 24
Cycle averaged <aa >
Fig. 5 The cycle averaged sunspot number versus the cycle
averaged <aa> . Note the data from 1868- 1900 and
195^-1977 show much the same relationship as the
data from 1900-195**.
Cycle
average
<R>
00
—
0
90
80
—
0
70
60
50
O
0
X
40
)P
30
x 1
1 1 ol
1
1 1 1
1 1 1
8 10 12 14 16 18 20 22 24 26 28 30
Preceeding Late Cycle Activity
Fig. 6 A comparison between the cycle averaged sunspot number and
the average of the activity during the first, second and
third year before the minimum of the preceding sunspot cycle,
The circles and crosses have the same meaning as in Figure S
A - 14
The relationship in Figure 6 cannot, of course, be used to predict mag-
netic activity in cycle 21. However, the magnetic activity early in the
cycle is roughly proportional to the sunspot number of that same cycle. This
is shown in Figure 7 where the cycle averaged sunspot number is plotted
against the average of the <aa> values for the fourth, fifth and sixth year
after the sunspot minimum which initiated the corresponding sunspot cycle.
The circles and crosses have the same meaning as in Figures 5 and 6. The
shaded region shows a range of predicted <aa> for cycle 21 which has been in-
cluded from an estimate of the mean sunspot number expected for cycle 21.
The cycle averaged sunspot number in cycle 21 was arrived at by noting that
the ratio of the cycle averaged sunspot number to the maximum sunspot number
ranged from 0.^1 to 0.56 for the ten cycles from 1867 to 1976. The mean of
the ratios was .50 and the root mean square deviation from the mean was .Ok.
Assuming the next sunspot cycle maximum is 150, this gives a cycle averaged
value of Ik + 6. The estimate of the uncertainty in <aa> is made by eye from
the other points on the graph. The star marks the middle of the region of the
prediction as an aid to the eye.
Another useful relationship is obtained from Figure 8 which shows the
<aa> average for the three years before sunspot minimum versus <aa> average
for the fourth, fifth and sixth year after that same minimum. Note that the
activity after minimum is smaller than that before minimum in 8 cycles out of 9
1.2 Application to Cycle 21
In this section I will project the patterns discussed above to cycle 21.
A serious difficulty appears at once. If we are now entering the declining
phase of the 80 year cycle, the trend will be erratic and declining. How-
ever, since we cannot be sure if the 80-100 year variation is indeed cyclic,
(or if it is, when the minimum will come) we have no way of telling whether or
not the break in the trend in I960 represented the beginning of a decline.
Since the decline cannot be predicted, the discussion in the remainder of
this section will be made under the assumption that the trend remains at the
level of the last geomagnetic minimum in 1977- Needless to say, this is a
very shaky assumption.
Then assuming the trend remains constant at 20, the first approximation
to the activity in cycle 21 is given in Table I where the average shape given
in Figure 2 is simply added to the constant trend. These values can be re-
fined and checked by using additional aspects of the patterns discussed in
the previous section. For example, the average for the fourth, fifth and
sixth year after minimum is 28 + 3 in Table I, but from Figure 7 it is esti-
mated to be between 22 and 26. The best estimate then is about 25 or 26.
This agrees with Figure 8 in which it is shown that the late activity of
cycle 20 during which <aa> averaged 27 should be greater than the first half
of cycle 21. Now, since cycle 21 is an odd cycle, the last half of the cycle
is expected to be lower than in the first half. In Table I the average of
the last three years before solar minimum is 26-3 + 2-5- Since this period
should be lower than 25-26, the lower part of this range is more probable,
say perhaps 23 or 2^. Carrying this line of argument yet further, since the
first half of a cycle is expected to be lower than the preceding last half,
the activity during the first half of cycle 22 should be lower than 23 or 2k.
A - 15
Cycle
average
<R>
•hi' n
_-
T
1SLJ I L_L
J I I L
13 14 15
23 24 25 26
Same Cycle
27 28 29 30
16 17 18 19 20 21 22
Early Cycle Activity,
Fig. 7 A comparison between the cycle averaged sunspot number and the
average of the activity during the fourth, fifth and sixth year after
minimum sunspot number. In this figure minimum is counted as year
one. The solar and geomagnetic activity are in the same cycle. The
shaded region shows the predicted values for cycle 21 assuming the
maximum sunspot number is 150.
Fig. 8
Late
Cycle
Activity
M
/
26
/
— /
/
/
O
24
— /
/
/
n
— /O
/
20
-
/
18
/ o
16
-0 / O X
14
/
12
^L
10
8
1 1 F 1 1 1 1 1
1 1 1
12 14 16 18 20 22 24 26 28 30 32 34
Early Cycle Activity (Following Cycle)
A comparison between the average of the activity during the first,
second and third year before the minimum of a sunspot cycle and the
average activity during the fourth, fifth and sixth year after that
minimum. The dashed line indicates equal activity.
A - 16
Table 1
Table I I
Year
1978
1979
1980
1981
1982
1983
<aa>
23
27
27
28
29
32
Year
1978
1979
1980
1981
1982
<aa>
23 + 3
27 + 2
25 '
26
27
min - 3 yr
min - 2 yr,
min - 1 yr
29 + 3
29 + 3
22 + 2
ml n -
3 yr.
24-25
min -
2 yr.
23-24
mi n -
1 yr.
22
Since cycle 22 is an even cycle, the last half is expected to be higher than
the first half and the line of predictions is broken.
The final predictions are shown in Table II. Since all the assumptions
and uncertainties that have gone into them have been outlined, it is clear
that they are on very shaky ground. However, with our present knowledge,
they are the best that can be done. The contribution of this paper is to
provide a status report on our ability to predict geomagnetic activity. The
major difficulty stems from our lack of understanding of the 80-100 year
cycle. It is therefore important that the solar wind and geomagnetic activi-
ty continue to be monitored and studied during the coming period when the
sunspot cycle, the solar wind and geomagnetic activity are expected to
decl ine.
Acknowledgments
I thank Dr. Murray Dryer and Dr. Donald J. Williams and the Space Envir-
onment Laboratory, NOAA for their hospitality while this work was being car-
ried out. I also thank H. H. Sargent for interesting and informative dis-
cussions and Dr. JoAnn Joselyn for reviewing the manuscript.
A - 17
REFERENCES
Bartels, J. (1932): Terr. Magn. and Atm. Elec. , 37., 1.
Chernosky, E. J. (1966): J. Geophys. Res. , 71 , 965.
Eddy, J. A. (1976): Science, 192, 1189.
Feynman, J. and N. U. Crooker (1978): Nature, ^75 626.
Fraser-Smith, A. C. (1972): J. Geophys. Res. , 77, 4209.
Fritz, Hermann (1873): Verzeichnis beobachter Pol ar 1 ichten , We i n , Poland,
Akademie.
Gosling, J. T. , J. R. Asbridge, S. J. Bame (1977): J . Geophys . Res . , 82,
3311, 1977.
Newton, H. W. (19^8): Mon. Not, of the R. Astr. Soc. Geophys. Suppl. 5,
159.
Mayaud, P. N. (1973): IAGA Bull. 33.
Ohl, A. I. (1968): Problems of the Arctic and Antarctic, 2_8, 1 37 .
Russell, C. T. (1975): Solar Phys. , kl_, 259-
Russell, C. T. and R. L. McPherron (1973): J. Geophys. Res. , 78, 92.
Sargent, H. H. (1978): Conference Record, Vehicular Tech. Soc, 28th IEEE,
Vehicular Tech. Conference, Denver, Colorado.
A - 18
COMPUTER FORECASTING OF GEOMAGNETIC DISTURBANCES
T. V. Gai voronskaya and V. P. Kuleshova
Institute of Terrestrial Magnetism,
Ionosphere and Radio Wave Propagation
of the USSR Academy of Sciences
Moscow, USSR
The forecasting of geomagnetic disturbances by computer is con-
sidered. Disturbances caused by chromospher i c flares and active
regions on the solar disk are predicted. The solar data are used
to obtain the signs that precede the magnetic storms. The forecast
is accomplished by one of the methods of pattern recognition, allow-
ing about 70% of the flares and 30% of the active regions to be
recogn ized .
NTR0DUCTI0N
In this report we consider geomagnetic storms caused by chromospher i c
flares (Gai voronskaya and Kuleshova, 1977) and active regions on the solar
disk and try to forecast these storms by computer. The computer forecast
depends on defining the geoef f i ci ency of the chromospher i c flare or the active
region independently of the magnetic disturbance value. The flare or active
region is considered as geoeffective if it is followed by a magnetic storm.
Prediction consists of forecasting the storms according to the preceding signs
of the flares and active regions. The classification of the signs as geo-
effective and non-geoef feet i ve depends on correct recognition of the patterns
(Vapnik and Chervonenki s , 197*0- We make use of the "Kora" method (Bongard,
1967; Vanzvaig, 1973), the most simple one to realize.
FORECAST OF THE FLARE GEOMAGNETIC DISTURBANCES
In considering the geomagnetic disturbances caused by flares the list of
the chromospher i c flares during 19&7-70 (Solar-Geophysical Data) has been con-
sidered. We chose flares of importance 2B and more; the number of these
flares is 137- Each flare is described by its importance, duration, and posi-
tion on the solar disk in regard to the central meridian. For each flare, we
have noted the sudden ionospheric disturbance (SID) and the burst at 3000 MHZ,
if there are any. SID and radio burst are then described by their duration,
A - 19
intensity and type, and are connected with the flare by the time of commence-
ment.
All data have been distributed into three groups according to three types
of information (optical flare, SID, radio wave). The signs of geoef feet i ve-
ness and non-geoef feet i veness are chosen in each group. In the group of opti-
cal data the choice is made in the following way. The more prolonged and
intensive the flare, and the less its distance from the central meridian, the
more probable that the flare is geoef feet i ve . Therefore, some values of dura-
tion, longitude, and importance can be found to be geoeffective signs. The
choice of these signs is supported by means of comparison of durations, longi-
tudes, and importance of all flares. The duration, the longitude, and the
importance of the geoeffective flare are taken as signs of geoef feet iveness ;
no non-geoef feet i ve flares have a greater importance and duration or a lesser
longitude. By such comparison the region of geoef feet i veness for three
values, duration, longitude, and importance have been determined. In the same
manner, non-geoef feet i ve signs are found.
Figure 1 shows the regions of geoef feet iveness and non-geoef feet iveness
determined by the signs for each flare's importance. Longitudes are plotted
versus the durations of the flares. The geoeffective region has the dense
shade; the non-geoef feet ive region has no shade. It is impossible to separate
the flares that are not in these regions.
Similarly, the signs for SID and radio wave data are obtained. These
results are shown in Figures 2 and 3-
3. FORECASTING OF GEOMAGNETIC DISTURBANCES CAUSED BY ACTIVE REGIONS
The list of plages during solar minimum (1963-65) has been taken in
order to forecast geomagnetic disturbances. The plages are described by the
following data (the first three are given at the moment of passage of
central mer id ian) :
1. heliographic latitude
2. area in millionths of the solar hemisphere
3. intensity
h. development of the plage during the current transit of the disk
(1 = passes to or from invisible hemisphere, b = bears on disk,
d = d ies on d isk)
5. stage of the area evolution ( / = increasing, — = stable,
\ = decreasing, f = increasing and stable, etc.)
6. age in solar rotations
7. duration of plage in disk given in days.
All data are distributed into groups so that signs can be determined:
1. latitude, area, intensity
2. development of plage and its area evolution
3. age and duration in disk.
In the case of forecasting a geomagnetic disturbance, it is impossible to de-
termine the influence of each active region on the geomagnetic field. There-
fore the longitude band of plages is taken as the active region independently
of the solar hemisphere (N and S) . To determine signs, the plage with the
greatest area of each active region is taken into account. We consider 315
active regions with 1 58 geoeffective regions. Figure h and Table 1 show the
geoeffective and non-geoef feet ive signs of plages for the three groups of data,
A - 20
<iO 20
0 20 VO 60 80
longitude of flare (deg)
Figure 1. Geoeffective
and non-geoef feet i ve re-
gions, according to
longitude and duration of
flare.
Figure 2. Geoeffective and non-
geoeffective regions, according to
intensity and duration of SID.
intensivity
Figure 3- Geo-
effective and
non-geoef feet i ve
regions, using
radio wave data.
i 10
5-10
1-10-
Type l
after
1,5 iO3 2-105
flux (io-'WHz')
is a microwave simple burst; type 2 indicates a rise of intensity
the burst (microwave range); and type 3 is a microwave complex burst.
A - 21
50 ~
4J ^o
<u
"3
&
30 1
v, 20
feu) /o
o
QJ
: l
- : i
• i
/ /
/ int
' , 1.5
/ 2,5
/ 3,3,5/
Y /
~* / / /
j / /
//Vrf
/ \/r-> —J
^rrrv^7"<
^//^/
1000
3000
5000 Sp
Figure *t. Geoeffective and non-
geoeffectlve signs of plages for
the three groups of data.
Thus, the computer dist
flare or the active region i
greatest area belongs to the
the contrary, it is non-geoe
The obtained signs are verif
data (flares 1971-73, plages
casting storms by computer,
percent of the active region
small amount of data used.
Table 1 . Geoeffect
Geoeffective Signs
Plage's
development
Area
evol ut
b
- 1
b
- 1
b
- 1
b
- d
1
- 1
1
- d
Age
in
rotation
V
A
-/
/
/
r
Duration on
disk (in days)
15
h
5, 10-12, ]h, 15
)h, 15
9, 12, \k
5, 9, 13, \k
ributes the phenomena in the following way: the
s geoeffective if the flare or the plage with the
geoeffective region for some group of data; on
ffective if it gets into a non-geoef feet i ve one.
ied with data that are not in the primary list of
1966-67). It confirms the possibility of fore-
The "Kora" method allows recognition of about 30
s and 70 percent of the flares, in spite of the
ive and Non-Geoef feet i ve Signs of Plages
Non-Geoef feet i ve Signs
Plage's Area
development
b - 1 -\
b - d /—
1 - d /
1 - d \
ion
evol ut ion
Age in
rotation
1
2
3
Duration on
disk (in days)
3, 6, 9
3, h, 8
A - 22
REFERENCES
Bongard, M. M. ( 1 967) : Problem of recognition, Nauka, Moscow.
Ga i voronskaya , T. V. and V. P. Kuleshova (1977): The forecasting of flare
magnetic disturbances by computer. In: Ionospheric disturbances and
methods of their forecast, Nauka, Moscow, 168-173-
Solar-Geophysical Data, Boulder (1963-73).
Vantsvaig, M. N. (1973): Algorithm "Kora" of teaching the pattern recognition
In: Algorithm of teaching the pattern recognition, Soviet Radio, Moscow.
Vapnik, V. N. and A. Ya. Chervonenkis (197*0: Theory of pattern recognition,
Nauka, Moscow.
A - 23
INTERPLANETARY MAGNETIC FIELD AND POLAR CAP
MAGNETIC DISTURBANCES: USING THE DATA FOR PREDICTION
OF AURORAL ELECTROJET ACTIVITY
O. A. Troshichev
Arctic and Antarctic Institute
Leningrad, 192104, USSR
N. P. Dmitrieva
Polar Geophysical Institute
Murmansk, 183023, USSR
B. M. Kuznetsov and V. P. Vasiliev
Institute of Physics, Leningrad University
Leningrad, 198904, USSR
The relationship between the IMF variations and geomagnetic
disturbances at the polar cap in summer and winter is analyzed.
The distribution of the space and amplitude characteristics of
the DP2, DP3, and DP 4 disturbances generated, respectively , by the
southward (B£s) 1 northward (BZftj) an<3 azimuthal (By) components of
the IMF are examined and a simple method for their separation is
proposed. The DP2 disturbances at the polar cap in summer precede
substorm activity, while similar disturbances at the polar cap in
winter develop synchronously with the westward auroral electro jet.
The indices of the IMF and polar cap magnetic activity suitable
for substorm prediction are developed.
The southward component of the IMF is the most significant parameter af-
fecting magnetospheric activity (Pudovkin et al., 1977; Kamide et al. , 1977).
The variability of the IMF seems to be another geoefficient characteristic
(Garrett et al., 1974). In order to forecast magnetospheric substorms, it is
necessary to determine effective precursors of substorms, not only in the IMF
characteristics but also in the ground magnetic data. The most suitable pre-
cursors are the polar cap magnetic disturbances induced as a result of perma-
nent interaction between the IMF and geomagnetic field (Nishida, 1968; Sval-
gaard, 1968; Mansurov, 1969; Iwasaki , 1971; Mishin et al. , 1973; Friis-
Christensen and Wilhjelm, 1975; Kuznetsov and Troshichev, 1977; and Levitin
et al., 1977). The DP2 disturbances are related to the southward component
(Bz < 0) of the IMF. The others are concerned with the northern or the azi-
muthal components of IMF (the DP3 and DP4 disturbances, respectively, accord-
ing to terminology by Kuznetsov and Troshichev (1977)). The main difficulty
in applying the DP2 variation to predictions is the problem of their separa-
tion from other polar cap magnetic disturbances.
A - 2*1
X = X +
KxxBx +
KXYBY
+
KxzBz
Y = Y +
1SrxBx +
KYYBY
+
KYZBZ
Z = Z +
KzxBx +
KZYBY
+
KzzBz
In this paper we analyze the relationship between the IMF parameters and
polar cap magnetic disturbances and propose a simple procedure for estimating
the disturbance intensity of the southward component of the IMF. New indices
of the polar cap magnetic activity and the IMF characteristics are examined.
1. DATA AND METHOD OF ANALYSIS
To analyze individual events we have used the magnetograms of five sta-
tions in the northern hemisphere (Alert, Resolute, Mould Bay, Godhavn, and
Baker Lake) , three stations in the southern hemisphere (Vostok, Dumont
d'Urville, and Mirny), and IMF observations obtained from the IMP-3 satellite
for July and August 1965. The correlation analysis was based on the hourly
values of the three components of the geomagnetic field for the same stations
and the Interplanetary Medium Data Book (King, 1977) for the period of July-
August, 1965 and 1966.
In the case of a three-dimensional distribution of probabilities, the
regression relation between the Bx, By, Bz components of the IMF and X, Y, Z
geomagnetic elements for a given station for each hour UT can be represented
as follows (Troshichev and Tsiganenko, 1978) :
(1)
where the K's are the regression coefficients and X, Y, Z are hourly values
of the three elements averaged for the period of July-August, 1965 and 1966.
From the regression coefficients and the values of X, Y, Z, it is possible to
obtain the direct relationship between the IMF components and the 6x, 6y, 6z
elements of the geomagnetic disturbance vector at each station and to con-
struct the appropriate distribution of 6F = /(6x)2 + (6Y)2 ancj the equiva-
lent current systems.
2. THE RELATIONSHIP BETWEEN THE IMF VARIATIONS AND
POLAR CAP MAGNETIC DISTURBANCES DURING SUMMER
We have examined the distribution of disturbance vectors, 6F, and the
current systems for different values of the IMF components. The current sys-
tem for the condition Bx = By = 0, Bz = -ly is shown in Figure 1(a). There
is a typical two-vortex DP2 current system with sunward currents near the
pole. The focuses of these vortices are located at latitudes $ ' - 75°-78°,
when Bz = -ly.
In the case of the northward (BZN) component (Bx = By = 0, Bz = ly), the
DP3 shows a two-vortex current system (Fig. 1(b)) in agreement with the re-
sults of Maezawa (1976) and Kuznetsov and Troshichev (1977) . In this system,
currents flow in the opposite direction; that is, currents are anti-sunward
near the pole. The focuses of the DP 3 current vortices are located at lati-
tude $' - 80°. Maximum values of 6F and maximum current intensity are ob-
A - 25
(a)DP2 (Besm*-iY)
ij
(6)»P* (BgSM*2r)
Summer
06 /<S
1 L*
(C)DP4 (&„,*-& Summer (d)l>P2(ltM«-i*) ^
Winter
Q6 06
00 MLT
Figure 1. The magnetic disturbances related to the IMF component variations:
(a) DP2, (b) DPo, (c) DP4 at the summer polar cap and (d) DP2 at the winter
polar cap.
served at daytime at latitude $ ' - 85°. The intensity of the current de-
creases rapidly in the equatorward direction.
The equivalent current system of DP4 disturbances, related to the azi-
muthal component of the IMF (Bx = Bz = 0, By = -Iy) is shown in Figure 1(c).
As distinct from the DP2 and DP3 systems, the DP4 equivalent system consists
only of one polar-cap current vortex connected with the polar electrojet in
the daytime cusp region. At latitudes lower than those of the cusp, there is
a tendency towards formation of the second vortex in the day sector.
The influence of the radial (Bx) component of the IMF at the geomagnetic
field is negligible almost everywhere. The correlation coefficients are near
zero for all hours UT, and the regression coefficients differ from zero only
A - 26
in the daytime cusp region. We interpret such regularity as being a result of
the close relationship of the Bx and By components within the framework of the
IMF sector structure.
The ionospheric current systems of the DP2, Dp3/ an<3 DP 4 disturbances may
be generated as a result of field-aligned currents flowing in and out of the
ionosphere. Troshichev and Gizler (1978) have computed the ionospheric ef-
fects produced by field-aligned currents using the Triad data (Iijima and
Potemra, 1976a, b) and a realistic model of the ionospheric conductivity (Van-
yan and Osipova, 1975) . The results obtained by Troshichev and Gizler show
that systems of the ionospheric electric fields and Hall currents generated
by field-aligned currents are in good agreement with the experimental data on
electric fields and current systems of the DP2/ DP-,/ and DP. disturbances.
DEPENDENCE OF THE DP2 AND DP 3 DISTURBANCE
INTENSITY ON THE Bz COMPONENT
According to Kuznetsov and Troshichev (1977) , the dependence of both DP?
and DP 3 disturbances on the magnitude of the vertical component Bz may be re-
garded as linear. The straight line which represents this dependence will
intersect the Bz axis at the point Bz - 1.5y. This conclusion is confirmed
by the present analysis.
Figure 2 shows the relationship between the intensities of DP2 and DP3
disturbances at the polar station Alert during periods of low magnetic ac-
tivity (AE < 120y) for different directions of the azimuthal component
» y.i>o
AE< 120 J
too-
i -t '4 -i to /i a i i g f
DP, ,
*FM,r /
* / . « ' aor
•// a
* •• */f * ■ CO-MO*-
# »* 7,'* • joo-soor
rfiLtf
4 6 t lit J
(a)
Figure 2. The relationship between the magnitude of the Bz component of the
IMF and the intensities of DP2 and DP-, disturbances at the nearpole station
Alert during the periods of low (a) and high (b) magnetic activity.
A - 27
(B,
0 and By >
0)
The solid lines represent the linear dependence obtained
by a least squares fit to the whole array of data, and the dotted lines repre-
sent dependences obtained separately for Bz > 0 and Bz < 0.
As Figure 2 includes data for all hours, we have examined the dependence
6F(BZ) for local morning, noon, evening, and night sectors separately. Our-
analysis shows that the linear relation between the Bz component of the IMF
and the DP2 and DP., disturbances is valid for any local time, but the charac-
ter of this relationship changes from day to night. Approximating the depen-
dence 6F(BZ) by
6F = K,
+ KiBz
(2)
we obtain the results presented in Table 1 (where BQ7 is the: value of Bz for
|«P| = 0) .
Table 1. The parameters of the linear relation between the Bz component of
the IMF and the DP2, DP 3 disturbances
morning
noon
evening
night
overall
(Fig. 2)
k0(y)
-13
-50
-29
-28.5
-30
K
15
20
17
19
18.5
B0z(y)
0.9
2.5
1.7
1.5
1.6
It may be seen that for fixed Bz values, the daytime intensity of the
DP2 disturbances is twice that of the dawn- time one. But in any case the mag-
nitude 6F appears to be equal to zero only for the northward component
Bz - (It 2.5)y- This agrees with the results of Maezawa (1976) and Kuznetsov
and Troshichev (1977) . The influence of the azimuthal components on the re-
lationship 6F(BZ) may be observed only in the daytime sector, where the inten-
sity of the DP2 disturbances tends to be higher for By > 0 than for B„ < 0.
It is significant that the intensity of the DP2 and DP3 disturbances in
the summer polar cap does not show obvious dependence on the activity of the
auroral electrojets. According to our results, the pattern of the function
6F(BZ) is the same for both low (Fig. 2(a), AE < 120y) and high (Fig. 2(b),
AE > 120y) activity.
Thus we conclude that the intensity of DP2 and DP3 disturbances in the
summer polar cap is determined mainly by the Bz component and therefore the
DP2 and DP-, disturbances in the summer polar cap may be a good indicator of
this IMF component.
4.
VARIATION OF THE RESIDUAL GEOMAGNETIC FIELD (S^ VARIATION)
q
The values X, Y, Z in equation (1) represent the geomagnetic field re-
maining after exclusion of variations generated by the IMF components (if the
linear relation between the IMF parameters and geomagnetic disturbances is
real) . Our analysis shows that the X~, Y, Z~ elements undergo a regular varia-
A - 28
tion with respect to their mean daily values. This variation may be presented
by a two-vortex current system similar to that of the DP2 disturbance (Fig.
3) . However, the variation of the residual geomagnetic field has evidently
another origin than the DP2 variation as (1) it is observed after the exclu-
sion of variations related to the IMF and the pattern is the same for both
Bz < 0 and Bz > 0, and (2) it is a daily variation.
We suppose this variation to be identified with the sP variation by
Nagata and Kokubun (1962) . It may result from the stationary magnetospheric
convection due to the nonmagnetic interaction of the solar wind with the mag-
netosphere. In accordance with the hypothesis of Axford (1969), the mechanism
of the quasiviscous friction may be proposed as a basic one in this inter-
action.
5. ESTIMATION OF THE ELECTRIC FIELDS OF THE
SP VARIATION AND THE DP2, DP3 DISTURBANCES
If the magnetic disturbances in the summer polar cap are generated by the
ionospheric Hall currents, the intensity of currents and therefore the elec-
tric field E may be easily estimated by
E(mV/m) -
6F
2ttZ
10 (Y)
(3)
where <5F is the magnitude of the magnetic disturbance and E is the Hall iono-
spheric conductivity, E - 10 mhO.
For the sP variation, when 6F is near 50y near the pole we obtain the
dawn-dusk electric field, E - 8 mV/m. For DP2 disturbances, the estimation
gives also the dawn-dusk field, E - 4 mV/m for Bz = -Iy and the growth of
this field is about 4 mV/m per Iy increase of the southward component BZs»
In the case of the DP-, disturbance, the electric field has the opposite di-
rection (dusk-dawn) with a maximum intensity in the daytime cusp region equal
(a)fl(a,
18
(V *%***> 0)
06 ft
■nf
00 MLT
iOO
Figure 3. The equivalent current systems of the residual geomagnetic field
variation (sP variation) for Bz < 0 (a) and Bz > 0 (b) .
A - 29
to about 8 mV/m for Bz = 2y . Estimated values appear to confirm the experi-
mental data.
In the case of the southern component of the IMF, the electric field of
DP2 and sPq variation are added together and the total field near the pole is
about 15 mV/m for Bz = -2y and E - 25 * 30 mV/m for Bz = -(4 * 5)Y. These
are typical values of the polar cap electric fields during periods of low and
moderate magnetic activity. In the case of the northern component BZN' tne
DP 3 electric field is cancelled by the S^ electric field until the northern
component becomes very large. That is why the DP2 disturbance pattern (or
sPq) may be observed at the polar cap for Bz = 0.
6. THE RELATIONSHIP BETWEEN THE IMF VARIATIONS AND
POLAR CAP MAGNETIC DISTURBANCES IN THE WINTER POLAR CAP
It has been noted already (Sumaruk and Feldstein, 1973; Friis-Christen-
sen and Wilhjelm, 1975) that the geomagnetic disturbances related to the
northward and azimuthal components of the IMF have maximum intensity in sum-
mer and tend to zero in winter. Our analysis leads to the same results. As
the field-aligned currents seem to be the main source of the DP2 and DPo dis-
turbances (Troshichev and Gizler, 1978) , the evident seasonal dependence of
these disturbances indicates that the occurrence and intensity of the daytime
cusp field-aligned currents is regulated by the ionospheric conductivity near
the pole.
The seasonal dependence of the DP2 disturbances is not so clear. Ac-
cording to a common point of view, they may be observed in the winter polar
cap as well as in the summer one. However in this case, the question arises
about the origin of the DP2 disturbance under conditions of low conductivity
in the winter ionosphere.
To solve this problem we analyzed the development of disturbances at
stations in botn the summer (Alert) and winter (Vostok) polar caps, when the
Bz component of the IMF turns to the south. The onset of the southward Bzs
component appears not to affect the geomagnetic field at Vostok until the
substorm begins, in contrast with the summer polar cap where DP2 disturbances
start 10-20 minutes after Bz turns to the south and only then does the sub-
storm develop. We noted 110 events of DP2 disturbances at Alert during July-
August 1965, but synchronous geomagnetic variations at Vostok were found in
only 23 events. Moreover, only 8 of them occurred when the AE-index was be-
low 100 y and for the other 15, the activity index was higher. This allows
us to conclude that there is a close connection between the development of
auroral electro jets and the occurrence of "DP2" disturbances in the winter
polar cap.
The results of the correlation analysis confirm this conclusion- We
calculated the regression coefficients and constructed the appropriate cur-
rent systems for disturbances in the winter polar cap related to the BZg com-
ponent (Fig. 1(d)) and for disturbances in both summer and winter polar caps
related to the westward electrojet (Fig. 4) .
The current patterns in Figures 1(a), 1(d), and 4 show the following.
The equivalent current systems of the polar cap disturbances related to the
westward electrojet are similar in summer and in winter (Fig. 4) . The equiv-
alent current system of the "DP2" disturbances in t.ie winter polar cap
A - 30
(a) N
(81*
18
-06
Figure 4. The equivalent current systems of the magnetic disturbances re-
lated to the westward electro jet at the summer (a) and winter (b) polar cap.
(Fig. 1(d)) differs from the standard DP„ system (Fig. 1(a)) but is similar to
systems in Figure 4. Taking into account the low conductivity and therefore
the small contribution of the ionospheric currents to the winter polar cap
disturbances, we conclude that the distant effects of the field-aligned cur-
rents are represented in Figure 1(d) and Figure 4(b). (The same interpreta-
tion is valid for disturbances in the summer polar cap related to the west-
ward electrojet, Figure 4(a).)
This means that the field-aligned DP2 currents in the winter polar cap
are closed only through the highly conducting auroral oval. If the ionospher-
ic conductivity in the auroral oval is as low as in the polar cap, the DP2
field-aligned currents will close up. As the increased conductivity in the
auroral oval depends directly on the substorm activity, the disturbances in
the winter polar cap due to DP2 field-aligned currents will be seen only dur-
ing the substorm development.
On the basis of these results it may be concluded that the "DP2" dis-
turbances in the winter polar cap cannot be used as precursors of the auroral
electrojet activity.
7. PROCEDURE OF THE FORECAST INDICES DERIVATION
Figure 1 shows that the fields of the DP , DP3
The geomagnetic disturbance vector 6F is
and DP* disturbances are
most homogeneous near the pole,
directed approximately from dawn to dusk in the case of the DP2 and DPo vari-
ations, but it lies along the noon-midnight meridian under the influence of
the azimuthal component of the IMF. Therefore we can assume that near the
pole at any moment of universal time (UT) , the projection of the 6F on the
axis 0600-1800 LT corresponds to the disturbances generated by the north-south
A - 31
F.
X
(Bz»
=
dX.
i
sin a . -
X
dY. cos
X
a .
X
F.
l
<V
=
dX.
i
cos a . +
X
dY . sin
X
a .
X
a .
X
=
A .
X
+ (UT) . «
15°
(Bz) component of the IMF, while the projection on the axis 1200-2400 LT cor-
responds to the disturbances due to the azimuthal (By) component, that is, in
the northern hemisphere.
(4)
where A. is the geographical longitude and dX and dY are the deviations of the
X and Y elements from their quiet level.
According to equation (4), the value F-j^Bj-) is positive when B^ < 0 (the
disturbance vector directed from dawn to dusk) , and is negative when B„ > 0
(direction to dawn); the value F^(By) is positive when By > 0 (direction to
noon) and is negative when By < 0 (direction to midnight) . The values dX and
dY were determined for every three minutes. The quantities F^ calculated
according to equation (4) were summarized for 15 minutes:
VV =1 W; VV -I Fi(V (5)
The magnitudes of F^ attributed to the end of the appropriate 15-minute in-
tervals were plotted on a graph. Intervals of 15 minutes duration were chosen
for the reason that these impulses in the IMF appear to be the shortest time
period for which polar cap magnetic variations may be traced (Garrett et al. ,
1974; Kuznetsov and Troshichev, 1977) .
In order to take into account the variability of the polar cap geomag-
metic field within the 15-minute intervals, we calculated the successive
differences
AX. = dX. - dX. -, AY. = dY. - dY. , (6)
x x x-1 x x 1-1
On the basis of these differences (defined with regard to their signs)
the quantities 8Fj_ and Ff were computed from
6F. (B„) = AX. sin a. - AY. cos a.
l Z x x x x
6F. (B„) = AX. cos a. + AY. sin a. (7)
x Y x x x x
F' =
AF„ )6f.
E L x
S At At
where At = 15 minutes. Thus for every 15-minute interval we have four char-
acteristics: F£ (Bz) / F£ (Bz) , and F^ (By) , F- (By) • The first pair represents
the 15-minute sum of the disturbance vectors and the 15-minute averaged rate
of change of these vectors for DP2 (when Fy > 0) or DP3 (when Fy < 0) dis-
turbances; the second pair represents the similar quantities for the DP 4 dis-
turbances. The signs of the Fy_ and F£ may be the same as well as opposite.
For example, the intensity of the DP2 disturbance (Fy_ (Bz) > 0) within the
15-minute interval can either increase (Fy (Bz) > 0) or decrease (Fy (Bz) < 0) .
For the interplanetary magnetic field, the 15-minute sum of the south-
ward component (^Bzs) and the 15-minute sum of the negative gradients of the
vertical component (} (-SB^) ) were likewise determined.
The IMF data and magnetograms of the observatory Alert for July 1965
were used in our analysis.
A - 32
EFFICIENCY OF THE FORECAST INDICES
We examine the relationship between the AE-indices of the substorm ac-
tivity and the values £bzs, £(-6Bz), Fs (Bz) , F£(BZ), FE(By) and Fi (By) for 25
days of July 1965. The first peculiarity which is obvious from the examina-
tion is the following: the rise of the AE-index almost always succeeds the
increase of the values of £BZS • There is a certain similarity between the
time course of the 2.BZS an *-^e changes in the AE-index. However, sometimes
the parameters £(-6Bz) seem to be more effective. Figure 5 gives an example
of such an event (see the period 1500-1800 UT, July 13) . To take into ac-
count these situations, it is reasonable to examine any combination of ^BZs
and V(-6BZ). In our analysis we take the product
ff(V = I Bzs ' I (-5V (8)
Unfortunately in many cases, the parameters a(Bz) are less clear than TBZg.
We consider the sum of these values where £bzs and £(-5Bz) are given dif-
ferent weights, to be a better parameter.
Among the polar cap magnetic characteristics, the value F^ (Bz) is the
most effective for forecasting. The intensive enhancements of the magnitude
of F<p (Bz) are followed by magnetic substorms with a time delay of 0.3-3
hours. After the decrease of Fy (Bz) , there is a decrease of activity in the
auroral zone. Apparently there is a threshold for the response of Fy (Bz)
about the value of 200y: the substorms do not develop when F^ (Bz) is below
this quantity. This threshold indicates that the S? variation contributes
to the value of F^.
6-7 1965
&vr
Figure 5. The relation between the AE-indices of substorm activity and various
characteristics of the IMF and the polar cap magnetic activity, July 13, 1965.
A - 33
It is typical that the correspondence between AE and F^ (B„) is present
not only in isolated substorms (which develop on the background of the quiet
geomagnetic field) , but also in cases of the substorm sequence, when maxima
are observed one after another with periodicity about one hour or more. Some-
times the striking similarity is seen even in such details as the time se-
quence and shape of the small spikes.
The characteristic F£ (Bz) examined separately from Fy (Bz) appears to be
poorly correlated with AE indices. The product of the values Fy (Bz) and
F£(BZ) (that is the PC (Bz) -index) gives the better result, because almost
every magnetic substorm seems to be preceded by enhancements in the value of
PC. But this characteristic undergoes constant changes in magnitude and in
sign and therefore it is difficult to use for forecasting.
Figure 5 shows also an unusual instance in which a very intensive en-
hancement of all values of the southward component of the IMF (^Br^g, a (B„) ,
Fj (Bz) , PC(BZ)) is not followed by any activity in the auroral zone. It may
be assumed that in this case, the auroral electro jet activity occurs at lati-
tudes higher than typical auroral zone latitudes.
The values related to the azimuthal components F^ (By) and F^ (By) axe
evidently useless for predicting. In any case they do not appear to cause
changes in the above regularities.
For 25 days of July 1965, we recorded 46 substorms with the intensity of
more than 200y (according to AE-indices) . This number includes the isolated
bays as well as intensive peaks of activity in the substorm sequences. The
results of the analysis are presented in Table 2, where all events and pre-
dicted substorms (on the basis of the polar cap data) are shown.
Table 2. The results of forecast analysis.
Indices of the
Amount of subs
torms
Amount of
polar cap
magnetic activity
all
examined
with
precursors
without
precursors
false
precursors
FZ<BZ>
Fz(V * F£<Bz>
Both indices are used
46
46
46
40
39
41
6
7
5
11
15
5
9. CONCLUSIONS
From the above results, it is concluded that most (>85%) moderate and
large substorms can be predicted on the basis of the IMF data as well as the
polar cap magnetic variations. The characteristics related to the southward
component of the IMF can be used as substorm predictors. The method proposed
in the present study will not predict those substorms which develop under the
northward component of the IMF. This method may also be used for diagnosis
of the IMF sector structure.
Acknowledgments. We thank Dr. N. F. Ness whose interplanetary magnetic
field data were used in this paper.
A - Ik
REFERENCES
Axford, W. I. (1969) : Viscous interaction between the solar wind and the
Earth's magnetosphere. Planet. Space Sci. , 12:45.
Friis-Christensen, E. , and J. Wilhjelm (1975) : Polar cap currents for dif-
ferent directions of the interplanetary magnetic field in the Y-Z plane.
J. Geophys. Res. , 80:1248.
Garrett, H. B., A. J. Dessler, and T. W. Hill (1974): Influence of solar
wind variability on geomagnetic activity. J. Geophys. Res., 79:4603.
Iijima, T. , and T. A. Potemra (1976a) : The amplitude distribution of field-
aligned currents of northern high latitudes observed by Triad. J.
Geophys. Res., 81:2165.
Iijima, T. , and T. A. Potemra (1976b) : Field-aligned currents in the dayside
cusp region observed by Triad. J. Geophys. Res., 81:5971.
Iwasaki, N. (1971) : Localized abnormal geomagnetic disturbances near the
geomagnetic pole and simultaneous ionosphere variation. Rep. Ionosph.
Space Res. Japan, 25:163.
Kamide, Y. , P. D. Perreault, S.-I. Akasofu, and J. D. Winningham (1977): De-
pendence of substorm occurrence probability on the interplanetary mag-
netic field and on the size of the auroral oval. J. Geophys. Res.,
82:5521.
King, J. H. (1977) : Interplanetary medium data book. Greenbelt, NSSDC,
N 77-04.
Kuznetsov, B. M. , and 0. A. Troshichev (1977): On the nature of polar cap
magnetic activity during undisturbed periods. Planet. Space Sci., 25:15.
Levitin, A. E. , B. A. Belov, R. G. Afonina et al. (1977): Three-dimensional
current systems of geomagnetic field variations in north polar cap con-
nected with component of the IMF. Preprint IZMIRAN, N 17 a.
Maezawa, K. (1976) : Magnetospheric convection induced by the positive and
negative Z components of the interplanetary magnetic field: quantitative
analysis using polar cap magnetic records. J. Geophys. Res., 81:2289.
Mansurov, S. M. (1969): New data about relation between space and Earth mag-
netic fields. Geomagn. Aeronomy, 9:768.
Mishin, V. M. , A. D. Bazarzhapov, E. I. Nemtsova et al. (1973): Influence of
the interplanetary magnetic field on magnetospheric convection and elec-
tric currents in the ionosphere. In: Substorms and magnetospheric dis-
turbances, Nauka, Leningrad, 191.
Nagata, T. , and S. Kokubun (1962): An additional geomagnetic daily variation
(sP -field) in the polar regie
Ion. Space Res. Japan, 16:256,
(sP -field) in the polar region on a geomagnetically quiet day. Rep,
Nishida, A. (1968) : Coherence of geomagnetic DP2 fluctuations with inter-
planetary magnetic variations. J. Geophys. Res., 73:5549.
Pudovkin, M. I., V. P. Kozelov, L. L. Lazutin, 0. A. Troshichev, and A. D.
Chertkov (1977) : Physics principles of magnetospheric disturbance
forecasting. Ed. S. I. Isaev, Nauka, Leningrad, 312 p.
A - 35
Sumaruk, P. V., and Feldstein, Ya. I. (1973): IMF sector structure and geo-
magnetic disturbances in the nearpole region. Kosmitch. Issled., 9:155.
Svalgaard, L. (1968) : Sector structure of the interplanetary magnetic field
and daily variation of the geomagnetic field at high latitudes. Danish.
Meteor. Inst. Geophys. Paper, R-6.
Troshichev, 0. A., and V. A. Gizler (1978): Field-aligned electric currents
and polar magnetic disturbances. In: Geomagnetic Research, Moscow, N
23, 24.
Troshichev, 0. A., and N. A. Tsiganenko (1978): Correlation relationship be-
tween parameters of the interplanetary magnetic field and polar cap
magnetic variations. In: Geomagnetic Research, Moscow, N 24.
Vanyan, L. L. , and I. L. Osipova (1975): Conductivity of the polar ionosphere.
Geomagn. Aeronomy, 15:847.
A - 36
SHORT-TERM FORECASTING OF GEOMAGNETIC STORMS
ASSOCIATED WITH HIGH-SPEED SOLAR WIND STREAMS
M. Mishin, V. V. Shelomentsev, A. D. Bazarzhapov,
and L. P. Sergeeva
Siberian Institute of Terrestrial Magnetism,
Ionosphere and Radio Wave Propagation (SiblZMIR)
lrkutsk-33, P.B.**, USSR
At the front of high-speed solar wind streams, density
bursts are observed with peak values n >_ 10 cm" . Such bursts
produce a characteristic geomagnetic response in the polar cap.
In principle, this effect may be used to predict, 0.5-1 day
beforehand, the geomagnetic storms observed when the high-speed
part of the stream crosses the Earth.
1. INTRODUCTION
Global geomagnetic storms are usually classified as two types: sporadic
(flare-associated) and recurrent. Sporadic storms are distinguished by the
presence of a sudden commencement (SC) , small duration (-1-2 days), absence
of a 27-day recurrence, and coherence with cyclic variations of the Wolf num-
bers. Recurrent storms are characterized by the absence of SC, long duration,
and recurrence. They achieve the greatest frequency and intensity at the de-
cline of the solar cycle phase, 1-2 years prior to the epoch of solar minimum.
Available techniques for magnetic storm prediction are well improved only
for flare-associated storms, whereas for recurrent ones the improvement is
insufficient. This can be explained, probably, by the fact that for the
flare-associated storms a whole number of ground precursors is known: magnetic
effects (SC) and crochet (SFE) , ionospheric effects (SID), absorption effects
in the polar caps (PCA) , etc. At the same time obvious and distinct precur-
sors of recurrent storms are not well established, and the forecasting of
such disturbances is based on their recurrence that enables us to predict
only the successive storms (at multiples of 27 days after the initial one)
but not the initial storm of the succession itself.
Thus, there is no available technique for forecasting geomagnetic
storms with respect to recurrent storms. This is significant since the flare-
associated disturbances are only ~3~^ percent of the total number of storms
at solar cycle minimum and -10-30 percent at solar cycle maximum, i.e., the
recurrent storms are predominant. Therefore, a discovery of precursors of
A - 37
recurrent storms is extremely desirable.
In the present paper some possibilities for short-term forecasting of
both recurrent and flare-associated storms are discussed in terms of ground
geomagnetic observations in the high-latitude region.
RELATION OF RECURRENT STORMS TO HIGH-SPEED SOLAR WIND STREAMS
For a long time the possibility of hypothetical M-regions on the sun (a
term introduced by Bartels, 1932) as being the sources of recurrent geomag-
netic storms and displaying no apparent signatures on the solar disk was
discussed. Recently, it was stated that these storms are associated with the
high-speed solar wind streams (HS) whose formation takes place mainly in the
regions of the solar surface with open configuration of magnetic field lines
where the so-called "coronal holes" are observed in X-ray emissions (Krieger
et al., 1973; Neupert and Pizzo, 197**; and Gulbrandsen, 1975). In view of
this relation of recurrent storms to high-speed streams, improvement of geo-
magnetic storm forecasting should involve the following:
1. detection of coronal holes with the help of solar observations;
2. detection of HS in the interplanetary medium;
3. discovery of ground signatures of HS and of their precursors.
A technique for the direct observation of coronal holes is not well developed
as yet and sometimes requires special cosmic instrumentation. The detection
of the HS while it is passing from the sun toward the Earth is also possible
with the help of cosmic instruments, although in the recent paper of Roelof
et al. (1977), the possibility, uniting points (2) and (3) above, was shown
of detecting density jumps, surpassing HS (and the geomagnetic disturbance
prediction -1 day beforehand) by means of ground observations of the inter-
planetary radio scintillation (IPS).
We shall examine the possibility of detecting the precursors of HS using
ground geomagnetic observations. For this purpose it is necessary first of
all to consider the structure of HS. According to the available models by
Hundhausen (1972) and by Ivanov and Mikerina (197*0, HS has a complex struc-
ture in the form of alternating layers, differing in physical characteristics
and producing, according to Ivanov and Mikerina (197*0, different geomagnetic
responses. Nevertheless, we think that to improve the technique for the pre-
diction of storms, it is sufficient to divide HS into only two parts — a "core1
and a "periphery."
Figure 1 is a schematic illustration of the time variations of solar
wind velocity (V) , density (n) , IMF module (B) , and the Dst-index; all ob-
served when a typical HS passes through the Earth's orbit. At the front of
HS the enhancement of n and B of a burst type are observed, the n-burst sur-
passing the B-burst (this behavior of wind parameters in the typical stream
is wel 1 known) .
From the analysis of 36 HS detected in the 1967-68 data of STAC-B (1971)
and of King (1977), we have estimated the mean delay times of onsets of B,V
increase and the main storm phase decrease seen by Ds^ with respect to the
n-burst onset. It turned out that At (n,B) - 6 hours, At (n,V) - 12 hours,
At (n,Dst) - 2k hours, i.e., the beginning of the storm's main phase takes
place, on the average, a day after the onset of the n-burst. It should be
noted also that the occurrence of storms havinq considerable magnitude
A - 38
"periphery" \
"core"
Figure 1. Typical profiles of
velocity, V, density, n, a module
of the IMF, B, in the high-speed
solar wind stream and associated
geomagnetic storm in D_t index.
At is the delay time of the main
storm phase with respect to the
onset of the growth of n.
(Dst < -kOy in the maximum of the main phase) is observed in -80 percent of
the cases in the sample.
On the basis of these data, by "core" we shall mean the high-speed part
of a stream and by "periphery," the front region wherein V has background
values but n and B are enhanced (Fig. l).
Taking into account the time estimates given above, one can assume that
the possibilities of short-term forecasting of the main phase lie in the dis-
covery of specific responses of the magnetosphere and the ionosphere to
bursts of n and B.
The role of the IMF in the generation of magnetospher ic substorms and
storms is well known. According to a theoretical reconnection hypothesis by
Dungey (1961) and to numerous experimental studies, the most geoeffective
solar wind parameter is the south IMF Z-component. A technique for defini-
tion of geoef f iciency of streams (mainly flare-associated) and for the pre-
diction of geomagnetic storms made possible by the discovery of a regular
direction of the IMF Z-component observed in large-scale magnetic fields in
the solar photosphere, is described in detail in a monograph by Pudovkin et
al . (1977) and is, undoubtedly, of great interest (see also Rosenberg and
Coleman, 1978). However, it is reasonable as well to study the geoef f iciency
of wind density bursts.
The role of this parameter in ground geomagnetic disturbances is as yet
but little understood, although it is emphasized in some works. The relation
of n to DCF-di sturbances and to the initial storm phase SC has been estab-
lished (see, for example, Verzariu et al., 1972; Kane, 197^; Pudovkin et al.,
1977). In addition, Kane (197*0 has shown that the presence of high values
of n £ 10 cm": is one of the necessary conditions for development of the
main storm phase (along with the presence of the south IMF Z-component).
Correlation coefficients of Dc^ and n during the initial storm phase are
higher than of Dst and V (-0.8-0.9 and 0.2-0. h, respectively).
Since the onset of the main storm phase, associated with HS, is
A - 39
appreciably delayed with regard to the onset of the n-burst, a study of the
geomagnetic effects of wind density may provide the basis for predicting
storms about a day beforehand. Below we shall consider the results obtained
for this purpose from the analysis of high-latitude magnetic data.
3. A GEOMAGNETIC RESPONSE OF THE POLAR CAP
TO THE PASSAGE OF A HIGH-SPEED STREAM PERIPHERY
3.1 Analysis of Geomagnetic Indices
In order to reveal the high-latitude geomagnetic response to the HS
passage, it is reasonable, first of all, to examine the behavior of specific
activity indices. In the polar cap they are the index PC, derived from data
from stations near the pole ($ £ 85°) (see, for example, lijima and Nagata,
1972; Kuznetsov and Troshichev, 1977) and the index PE, from data of magneto-
spheric cleft projection stations ($ - 75-81°) (Shelomentsev and Mishin,
1977). These indices reflect the dynamics of polar disturbances such as
SqP, DP-2, PEJ and others, and yield, according to Shelomentsev and Mishin
( T977) , good results in the current forecasting of magnetic substorms (ex-
pansion phase) -1-3 hours beforehand.
A method of superimposed epochs was used for this analysis of the data
for 1967-68. Figure 2 presents the profiles of PC, PE, and Dst, averaged
over 20 streams where the zero time moment (t=0) is the onset of the main
storm phase in Dst.
The stable growth of the polar cap indices begins -6-10 hours prior to
t = 0. It is of interest to note that the index PE displays considerable
dynamics in the earlier period also. This may testify to the fact that the
PEJC(%)
Figure 2. Changes of polar cap
indices PC and PE before the main
phase onset in D t (a superimposed
epoch method for Z0 streams) .
kO
characteristic activity fluctuations in the magnetospher ic cleft zone begin a
long time before (of an order of a day) the main phase onset that is important
for predicting.
The results show evidence that the polar cap responds, in a definite man-
ner, to the HS passage (including its "periphery") before the onset of a geo-
magnetic storm related to HS. However, these data do not explain anything
about the effect of the wind density jump at the stream front. Therefore we
have selected 16 specific n-bursts that surpass the proper HS (its "core"),
i.e., observed during the background valuesof wind velocity (V - Vfa - con-
stant) and we have used a superimposed epoch method. The zero moment (t = 0)
corresponds to the n-burst onset. All bursts are reduced to a mean value of At
from the growth onset up to the maximum of n (contraction or expansion in the
time axis). Only the cases with At <, 10 hours were selected. A mean value
is <At> - 6 hours. Values of the H-component at stations near the pole,
Resolute Bay (N), and Vostok (S), were taken as a geomagnetic measure (a rough
analog of index PC). Results are given in Figure 3. It is seen that the
passage of the density burst through the Earth is, in fact, accompanied by
the enhancement of a transpolar current in the ionosphere.
Since the present sample corresponds to a stream "periphery" (<V> lies
within 380-390 km/s; i.e., it is practically constant during the time inter-
val under consideration), only the parameters n and B may be geoeffecti ve.
To clarify the role of the IMF, a profile of the Z-component is presented in
Figure 3- (For the convenience of comparison with geomagnetic data, the or-
dinate axis, Z$m, is reversed.) This figure shows that at the period when
t = -2 v +2 hours, Zg^ is southward and for t > +2 hours, it is northward.
For the reason given, the growth of H at t = -2 * +2 hours may be
associated with the presence of the southern IMF. However, the influence of
parameter n is also well seen from the inequality of values H at t < 0 and
ZSH<P
Figure 3. Changes of a transpolar
current in the ionosphere (H) , of
ZsM-component of the IMF and of
solar wind density (n) , derived by
the superimposed epoch method for
16 n-bursts at the HS-fronts. A
zero time moment corresponds to
the n-burst onset.
r (h)
A - k\
t > 0 at equal Zg^. For example, for Zc;^ = 0, H - 35y at t = -2 hours, and
H - 60y at t = +2 hours. On the whole, values of H at the increased values
of n are considerably higher than those before the burst. An additional
analysis in which the given sample was divided into two according to the pre-
dominant sign of Zs^ (southern or northern) supported this conclusion.
Thus, the behavior of polar cap indices testifies to the fact that the
magnetosphere responds, in a certain manner, to the passage of the "periphery"
of the stream where there is a density burst (as well as the growth of
modules and fluctuations of the IMF). According to the above data, the lead
time for forecasting storms associated with HS is not great (-6-10 hours).
However, these ciphers probably define only the lower limit as the indices
were based on data from only a few stations; i.e., they may not be represen-
tative. It would be reasonable to study the effect using more precise char-
acteristics like the equivalent current patterns based on data from the entire
available network of observatories. This could elucidate a type of current
system that produces the geomagnetic response of n-variations .
3.2 The Analysis of High-Latitude S-Currents
In order to draw the equivalent current patterns that describe the ef-
fect of solar wind parameters, we have used the data from a global network
of stations for 8 quiet summer days in 1968; the hourly values of solar wind
parameters (King, 1977); and a modified method of a spherical harmonic analy-
sis by Bazarzhapov et al. (1975). The original spectrum of spherical func-
tions that describes a magnetic potential and an external current function
10R.-Y V 2n + 1 /°F\ /rm . , m .,_Nnm / n\ fi\
J = " "T^A I n t 1 (R ^ (En COS mt en Sin mt)Pn (cOS 9) (1)
n m
involves 15 zonal and 14 tesseral harmonics. The coefficients E = {E™, e™}
were expanded in series by the solar wind parameters (density, velocity, and
IMF components) :
E = a0 + ain + a2V + a3Bz + a4By + ... (2)
where the dots involve multiplicative terms (products with respect to_ V ^nd
the IMF components describing the interplanetary electric field E = -V x B) .
The coefficients a: were determined by the least-squares method for each co-
efficient E separately. By means of equation (1), isolines, J;, were drawn,
representing the systems of equivalent currents. These are reflected by the
individual terms in the expansion equation (2) and describe the effects of n
(Sn currents) , V (6y currents) , etc.
The current patterns for 6y (at V = 4C0 km/s) , 5Z (at Bz = -3y) and
6y (at By = ky) are presented in Figure k. As expected, the 6y and 6Z systems
are similar to the SqP and the DP-2 currents. It is well known that the
southern IMF component affects the development of the DP-2 currents (Nishida,
1968; and lijima and Nagata, 1972), and, probably, the velocity effect is
caused by "viscous friction" mechanisms, which produce large-scale magneto-
spheric convection. The ionospheric reflection is represented by Hall cur-
rents of the SqP or DP-2 type (Axford and Hines, 1961). The <5y currents, as
distinct from 6.. and 6 , are zonal ones, in agreement with Fr i is-Chr istensen
V z > j
A - 42
6 18
Figure k. Equivalent 6-currents in
the polar region, reflecting the
effect of solar wind velocity
(6V at V = 'tOO km/s) and IMF
(6Z at Bz = -3y and 6y at By = %) .
Current lines are drawn for inter-
vals of lOkA.
and Wilhelm (1975), Mishin et al. (1975), and Sumaruk and Feldstein (1975).
The similarity of these patterns with the known ones indicates that this is
the correct technique for the computation of 6-currents. Such confidence in
the technique is necessary for understanding the unknown effects of solar
wind density.
Currents 6n are given in Figure 5 for two values: n = k cm"3 and 6 cm"3,
They are similar in form to the currents 6y and 6Z, i.e., to the S P and the
DP-2 currents. This probably shows evidence for the effect of "viscous
friction" mechanisms also. The value of the transpolar current is -30-50 kA
(ki loamperes) for the given values of n, and -80-90 kA at n - 10 cm"3 (the
latter is consistent with the minimal peak value observed in bursts at the
HS-f ront) . The value of the ground magnetic disturbance caused by currents
of similar strength is ^20-40y; i.e., it should be distinguished on
magnetograms with standard sensitivity (-5-10 y/mm) .
n = 4
Figure 5. Equivalent 6-currents
in the polar region, reflecting
the effect of solar wind density
(6n at n = k cm"3 and 6 cm"3),
g The interval between current lines
is 5 kA.
cm
n=6
cm
A - 43
k. CONCLUSION
From the analysis of the behavior of the geomagnetic indices PC and PE as
well as the computation of 6-currents in the polar cap produced by fluctua-
tions of different solar wind parameters, it is concluded that the density
bursts observed at the front ("periphery") of high-speed solar wind streams
result in characteristic geomagnetic responses. The 6n-current system is
similar in form to the SgP and DP-2 currents and has an appreciable intensity
at values n £ 5 cm . In principle, this effect may be used for the short-
term forecasting of geomagnetic (both recurrent and flare-associated) storms
with a lead time of the order of 0.5~1 day. Although the prompt computation
of the 6-currents is hardly possible at present, the results indicate that
the detection of 6n-di sturbances , which in - 80 percent of the cases are
precursors of strong storms (Dst - -hOj) can be realized with a more simple
treatment of magnetograms or indices from polar cap stations. Further de-
tailed studies are necessary for the development of this technique.
REFERENCES
Axford, W. I., and C. 0. Hines ( 1 96 1 ) : A unifying theory of high latitude
geophysical phenomena and geomagnetic storms. Can. J . Phys. , 39:1*03.
Bartels, J. (1932): Terrestrial magnetic activity and its relation to solar
phenomena. Terr. Magn . , 37:1.
Bazarzhapov, A. D., V. M. Mishin, and G. B. Shpynev (1975): A mathematical
analysis of geomagnetic variation fields. Gerl. Beitr. Geophys. 8*t:9l8.
Dungey, J. W. (1961): Interplanetary magnetic field and the auroral zones.
Phys. Rev. Lett., 6:^7.
Fri is-Christensen, E., and J. Wilhelm (1975): Polar cap currents for differ-
ent direction of the interplanetary magnetic field in the YZ-plane.
J. Geophys. Res., 80:12**8.
Gulbrandsen, A. (1975): The solar M-region problem — an old problem now
facing its solution? Planet. Space Sc? . , 23:1*»3-
Hundhausen, A. J. (1972): Coronal Expansion and Solar Wind. Springer-Ferlag,
Heidelberg-N.Y.
lijima, T., and T. Nagata (1972): Signatures for substorm development of the
growth phase and expansion phase. Planet. Space Sci . , 20:1095.
Ivanov, K. G., and N. V. Mikerina (197*0: A structure of the interplanetary
plasma streams and geomagnetic disturbances. In: Solar Wind and Mag-
netosphere, Moscow, IZMIRAN, p. 3 (in Russian).
Kane, R. P. (197*0: Relationship between interplanetary plasma parameters
and geomagnetic Dst« J. Geophys. Res. , 79:6**.
A - M
King, J. H. (1977): Interplanetary Medium Data-Book-Appendix, ed. by NSSDC/
WDC-A.
Krieger, A. S., A. F. Timothy, and E. C. Roelof (1973): A coronal hole and
its identification as the source of a high velocity solar wind stream.
Solar Phys., 23:123-
Kuznetsov, B. M., and 0. A. Troshichev (1977): On the nature of polar cap
magnetic activity during undisturbed periods. Planet. Space Sci . , 25:15.
Mishin, V. M. , A. D. Bazarzhapov, E. I. Nemtsova, G. V. Popov, and V. V.
Shelomentsev (1975): The effect of the IMF on magnetospher ic convection
and electric currents in the ionosphere. In: Substorms and Disturbances
in the Magnetosphere, Leningrad, Nauka, p. 191 ( in Russian) .
Neupert, W. M., and V. Pizzo (197*0: Solar coronal holes as sources of re-
current geomagnetic disturbances. J . Geophys. Res . , 79:3701.
Nishida, A. (1968): Geomagnetic DP-2 fluctuations and associated magneto-
spheric phenomena. J. Geophys. Res., 73:1795.
Pudovkin, M. I., V. P. Kozelov, L. L. Lazutin, 0. A. Troshichev, and A. D.
Chertov (1977): Physical Basis for the Magnetospher ic Disturbance
Forecasting, Len ingrad, Nauka (in Russian).
Roelof, E. C, B. L. Gotwols, D. G. Mitchell, W. M. Cronyn, and S. D. Shawhan
(1977): Use of interplanetary radio scintillation power spectra in pre-
dicting geomagnetic disturbances, preprint of Johns Hopkins University,
AFGL-TR-77-02AA.
Rosenberg, R. L., and P. J. Coleman, Jr. (1978): Solar cycle-dependent
north-south field configurations observed in solar wind interaction
regions, preprint No. 180A, University of California.
Shelomentsev, V. V., and V. M. Mishin (1977): A magnetospher ic cleft index
PE and short-term forecasting of the substorm breakup phase. Abstracts
of the Symposium on Geomagnetospher ic Physics, Irkutsk, p. 28 (in
Russian) .
"Solar-Terrestrial Activity Charts (STAC-B) for 1967- 1968," ed. by the
Science Council of Japan, under T. Obayashi (1971).
Sumaruk, P. V., and Y. I. Feldstein (1975): Magnetic field variations in the
polar cap. In: Substorms and Disturbances in the Magnetosphere,
Leningrad, Nauka, p. 170 (in Russian) .
Verzariu, P., M. Sugiura, and I. B. Strong (1972): Geomagnetic field varia-
tions caused by changes in the quiet-time solar-wind pressure. Planet.
Space Sci . , 20:1909.
A - hS
SOLAR CYCLE EFFECT OF 27-DAY RECURRENT GEOMAGNETIC STORM
T. ONDOH and Y. NAKAMURA
Radio Research Laboratories, Tokyo, 184, JAPAN
The 27-day autocorrelation coefficients of £K_ and mean iKp over
5 solar rotations have been computed at solar rotation numbers from
1550 (Aug. 1946) to 1975 (Feb. 1978). These results are compared
with the solar cycle variation of smoothed sunspot numbers.
The general features of the 18th sunspot cycle are very similar to
those of the 20th sunspot cycle. This fact suggests the 22 year
period as the basic solar cycle. In the declining phase of the 20th
sunspot cycle, 27-day autocorrelation coefficients of £Kp above 0.4
have continued from Dec. 1972 to Oct. 1976 being longer than those in
the 18th sunspot cycle. These recurrent geomagnetic disturbances
in the 20th cycle occur in association with long-lived coronal holes
and high-speed solar wind streams. The 27-day autocorrelation coef-
ficients of 2Kp above 0.4 occur for smoothed sunspot numbers ranging
from 82.2 to 6.3 in the declining phase of the 18th sunspot cycle.
This range of smoothed sunspot number for recurrent geomagnetic dis-
turbances in the 18th cycle is very close to that of 80.4 - 13.4 in
the declining phase of the 20th cycle except for the solar flare events
in August, 1972. Hence, we may forecast occurrences of long-lived
coronal holes, high-speed solar wind streams, and recurrent geomagnetic
storms by estimating time variation of the sunspot number.
1. Introduction
Newton and Milsom (1954) showed a close accordance between the averaged
sunspot curve and the averaged curve for geomagnetic storms, and also
reported recurrence peaks of the non-sc storms around +27 and +54 days.
Chernosky (1966) found from the superposition analysis of the daily magnetic
character figure Ci that the declining phase of the even sunspot cycle is
more active in geomagnetic activity than the ascending phase, and that the
converse is true for the odd cycle. Recently, long-lived coronal holes have
been identified as the origin of solar wind high-speed streams and their
associated recurrent geomagnetic disturbances (Krieger et al. ,1973, 1974 ;
Neupert and Pizzo,1974 ; Sheeley et al.,1976).
In this paper, we compare the smoothed sunspot number with the 27-day
autocorrelation coefficient of £Kp during Aug. 1946 to Feb. 1978, and
discuss on the prediction of recurrent geomagnetic storms and high-speed
solar wind by the time variation of smoothed sunspot number.
A - 46
2. 27-Day Recurrent Tendency of Geomagnetic Activity in the
Solar Quiet Period
The 27-day autocorrelation coefficient Ac(n) of ^Kp at the solar rotation
number of "n" over five solar rotations can be computed by
I |p(t) - P(t)|. J P(t+27) - P(t+27)
Ac (n) = 1
»
c2
2 t2,
• tJtf
(t+27) - P(t+27)
2 nl/2
P(t) =
27 x 5 t=ti
.£ P(t) , and P(t+27) =
27 x 5 t=ti
•Z P(t+27) , where P(t)
denotes the daily sum of three-hour geomagnetic activity indices, £Kp,
ti = 27 x (n - 3) + 1 and t2 = 27 x (n + 2) . Ac(n) is computed from ZKp
data observed during solar rotation number of (n - 3) to (n + 2) .
Fig. 1 shows 27-day autocorrelation coefficients of £Kp, mean £Kp over 5
solar rotations, and smoothed sunspot numbers from solar rotation number
(SRN) of 1550 (Aug. 1946) to 1750 (June 1961) . The time variation of sun-
spot number in Fig. 1 indicates that the sunspot cycle 18th ended around SRN
of 1653 (April 1954) . The 27-day autocorrelation coefficients of EKp
between SRN 1603 and 1650 are higher (above 0.4) than those in other periods.
This high recurrent tendency of geomagnetic activity occurs corresponding to
the decrease of sunspot number from 82.2 at SRN 1603 to 6.3 at SRN 1650, al-
though the 27-day autocorrelation coefficient deeply decreased down to 0.1
at SRN 1615 (June 1951) corresponding to a short term enhancement of the sun-
spot number or solar activity around SRN 1615. Except for the above period
between SRN 1603 and 1650, the 27-day autocorrelation coefficients are mostly
below 0.3 in the solar cycle 18th and 19th as shown in Fig. 1.
The time variation of smoothed sunspot number in Fig. 1 shows the 18th cycle
maximum of 151.8 in May, 1947, the minimum of 3.4 in April, 1954, and the
19th cycle maximum of 201.3 in March, 1958 respectively. The 27-day auto-
correlation coefficients of £Kp are higher than 0.4 from the middle of de-
clining phase of the solar activity to the vicinity of solar activity minimum
in the 18th sunspot cycle. However, there occurred no such effect in the
19th cycle untill June, 1961. The smoothed sunspot number in June, 1961 is
55.8 which is far below a half of the maximum in the 19th cycle (201.3).
Concerning this respect and also the maximum sunspot number, solar character-
istics in the 18th cycle are considerably different from those in the 19th
cycle.
Fig. 2 illustrates time variations of the smoothed sunspot number, mean
£Kp over 5 solar rotations, and 27-day autocorrelation coefficient of SIC
observed during SRN 1750 (June, 1961) to SRN 1975 (Feb. 1978). The time
variation of smoothed sunspot number in Fig. 2 shows a minimum of 9.6 at SRN
1795 (Oct. 1964), a maximum of 110.6 at SRN 1851 (Nov. 1968), and a minimum
of 12.2 at SRN 1950 (March 1976) respectively. The maximum sunspot number
of 110.6 in the 20th sunspot cycle (Aug. 1964 - March 1976) is about one
half of that (201.3) in the 19th cycle, and it is also smaller than the maxi-
mum sunspot number of 151.8 in the 18th cycle.
A - 47
SUIMSPOT CYCLE 18&19
SMOOTHED SUNSPOT NUMBER
30
25
20
15
10
MEAN EKp OVER 5 SOLAR ROTATIONS
27 DAY AUTOCORRELATION COEFFICIENT OF £KF
Fig. 1 Solar-cycle variations of the smoothed sunspot number, mean £Kp
over five solar rotations, and 27-day autocorrelation coefficient
of EKp during August, 1946 to June, 1961.
48
120
100
80
60
40
20
0
25
20
15
10
1750
1961. JUN.
SUNSPOT CYCLE 20
SMOOTHED SUNSPOT NUMBER
MEAN EKP OVER 5 SOLAR ROTATIONS
27 DAY AUTOCORRELATION COEFFICIENT OF ZKP
1950
1976 MAR
Fig. 2 Solar-cycle variations of the smoothed sunspot number, mean
ZKp over five solar rotations, and 27-day autocorrelation
coefficient of £K_ during June 1961 to February 1978.
A - k$
In the 19th sunspot cycle (SRN 1653 ; April 1954 - SRN 1793 ; Aug. 1964),
27 day autocorrelation coefficients above 0.4 of ZKp occur in a period be-
tween SRN 1769 (June 1962) and SRN 1793 (Aug. 1964) .corresponding to the sun-
spot number of 38 and 10 respectively. Thus, the high recurrent period of
geomagnetic activity in the 19th cycle is much shorter than that in the 18th
cycle. In the 20th sunspot cycle (SRN 1793 ; Aug. 1964 - SRN 1950 ;
March 1976) , the 27-day autocorrelation coefficient of £Kp once became above
0.4 between SRN 1880(Jan. 1971) and SRN 1884(May ,1971) , corresponding to
smoothed sunspot number decrease from 80.4 to 68.1, but it decreased down to
-0.09 at SRN 1899 (June 1972). Then, the 27-day autocorrelation coefficient
increased rapidly up to 0.4 at SRN 1906 (Dec, 1972).
This deep valley of 27-day autocorrelation coefficient of ZKp around June,
1972 results from a short-term enhancement of the smoothed sunspot number
which is associated with the solar active center causing the August event,
in 1972. The deep decrease of 27-day autocorrelation coefficient of ZKp
around June, 1972 in the 20th sunspot cycle (Fig. 2) is very similar to that
around June, 1951 in the 18th cycle (Fig. 1) which is also associated with a
short-term enhancement of the sunspot number. It should be noted that the
short-term degradation of 27-day recurrent tendency of the geomagnetic ac-
tivity occurs simultaneously with the sunspot increase halfway during the
sunspot declining phase in both of the 18th and 20th cycles.
The 27-day autocorrelation coefficients of £Kp were above 0.4 in a long
period between SRN 1906(Dec. 1972) and SRN 1958 (Oct. 1976) during which the
smoothed sunspot number decreased from 55.1 to 13.4. The high recurrent
period of geomagnetic disturbances in the 20th cycle is longer than those in
both of the 19th and 18th cycles. This is a remarkable thing in the 20th
sunspot cycle, together with a low value (110.6) of the maximum sunspot num-
ber. In summary, the general features of the 20th sunspot cycle are very
similar to those of the 18th sunspot cycle, but not to the 19th cycle, though
the maximum smoothed sunspot number in the 18th cycle is higher than that in
the 20th cycle. This fact suggests that the basic solar cycle is the 22
year period rather than the 11 year period.
3. Application of the 27-day Recurrent Tendency of the Geomagnetic
Activity to the Forecast of Solar-terrestrial Disturbances in
the Solar Quiet Period
o o
Solar images derived from Hell 304 A and Hel 10830 A spectroheliograms or
wideband XUV images during the Skylab mission (Bohlin and Rubenstein,1975 ;
Tousey et al.,1973) have revealed that coronal holes in low latitudes (so
called the M region) are the origin of solar wind high-speed streams and
27-day recurrent geomagnetic disturbances. Sheeley et al.(1976) have added
3 days to the occurrence times of both the coronal holes and solar wind
streams to maximize the correlation of the holes and high-speed streams above
600 km/sec with the geomagnetic disturbances as a sequence of 27-day Bartels
rotations. In Table 1, we compare solar wind velocities with smoothed sun-
spot numbers and 27-day autocorrelation coefficients of Z Kp from May, 1970
(SRN 1871) to May, 1973 (SRN 1911) in order to forecast the occurrence of
high-speed solar plasma streams and recurrent geomagnetic disturbances.
Solar wind data in Table 1 are taken from the Interplanetary Medium Data
A - 50
Book published by NSSDC/WDC-A (1977).
Table 1 Comparison of solar wind velocity, 27-day autocorrelation coeffi-
cient of ^Kp and smoothed sunspot number
SRN
Month/Day /Year
Ac(n)
Solar
Wind
km/sec
Smoothed Sunspot
Number
V
max
V
av
V .
mm
1871
1872
5/5 - 5/31/'70
6/1 - 6/27/'70
-0.01
0.06
669
706
398
420
291
266
105.8
105.3
1882
1884
2/26 -3/24/'71
4/21 -5/17/'71
0.47
0.40
696
678
441
408
300
310
74.4
68.1
1899
1900
5/30 -6/25/'72
6/26 -7/22/'72
-0.11
-0.09
485
510
378
377
290
285
70.5
68.2
1910
1911
1
3/23 -4/18/'73
4/19 -5/15/*73
0.50
0.49
i
785
797
572
583
342
351
42.7
40.7
_
The maximum velocity, average velocity, and minimum velocity of the solar
wind in a period of SRN 1911 are the highest of all solar wind velocities in
Table 1. The SRN 1911 belongs to the period of highly recurrent geomagnetic
activities ( Ac(n) > 0.4 ) which have continued long from Dec. 1972 to Oct.
1976. In fact, Sheeley et al. (1976) have shown high correlations of long-
lived coronal holes, high-speed solar winds, and recurrent geomagnetic acti-
vities during Jan., 1973 to Jan., 1976 in a familiar 27-day Bartels format.
At SRN 1899 and 1900, the three kind speeds of solar wind are the lowest of
all solar wind speeds in Table 1. This low-speed solar wind corresponds
well to the lowest 27-day autocorrelation coefficient of £Kp (-0.1) and
the solar active center producing the August event in 1972. The three kind
speeds of solar wind at SRN 1882 and 1884 are again higher compared with
those at SRN 1899 and 1900. This reflects well high values of the 27-day
autocorrelation coefficient of £Kp ( > 0.4) in a period between SRN 1880
and 1884. However, at SRN 1871 and 1872 (May - June, 1970) when the 27-day
autocorrelation coefficients of ^K- are below 0.1, solar wind speeds are
relatively high. This may result from random occurrences of solar flares
during the solar active phase of the 20th sunspot cycle, but not from coronal
holes. Thus, it becomes clear that long-lived coronal holes and high-speed
solar wind streams produce 27-day recurrent geomagnetic disturbances only
during the declining phase of the sunspot cycle.
In the declining phase of the 18th sunspot cycle, 27-day autocorrelation
coefficients of EKp above 0.4 occur for smoothed sunspot numbers ranging
from 82.2 to 6.3 except for the solar-flare events around June, 1951 (SRN
1651). Also, in the declining phase of the 20th sunspot cycle, 27-day
autocorrelation coefficients of £Kp above 0.4 occur for smoothed sunspot
numbers ranging from 80.4 to 13.4 except for the solar-flare events around
August, 1972 (SRN 1901). In summary, high-speed solar wind streams above
600-700 km/sec originating from low-latitude coronal holes caused recurrent
geomagnetic storms corresponding to smoothed sunspot numbers for about 80 to
10 in the declining phase of the 18th and 20th sunspot cycles, except for
solar flare events. Further comparative study between 27-day autocorrela-
tion coefficients of IK-, and smoothed sunspot numbers is needed to apply the
above results to the storm forecast in the solar quiet period.
A - 51
References
Bohlin, J. D. and D. M. Rubenstein (1975) : Report UAG-51, World Data
Center A for Solar - Terrestrial Physics, NOAA, Boulder, Colorado..
Chernosky , E. J. (1966) : Double sunspot-cycle variation in terrestrial
magnetic activity, 1884 - 1963, J. Geophysical Research, 71, 965.
Interplanetary Medium Data Book (1977) : National Space Science Data
Center, World Data Center A for Rockets and Satellites, NASA.
Krieger, A. S., A. F. Timothy, and E. C. Roelof (1973) : A coronal hole
and its identification as the source of a high velocity solar wind
stream, Solar Physics, 37, 469.
Krieger, A. S. , A. F. Timothy, G. S. Vaiana, A. J. Lazarus, and J. D.
Sullivan (1974) : Solar Wind Three, Edited by C. T. Russell, 132.
Neupert, W. M. and V. Pizzo (1974) : Solar coronal holes as sources of
recurrent geomagnetic disturbances, J. Geophysical Research, 79,
3701.
Newton, H. W. and A. S. Milsom (1954) : The distribution of great and
small geomagnetic storms in the sunspot cycle, J. Geophysical
Research, 59, 203.
Sheeley, JR. N. R. , J. W. Harvey, and W. C. Feldman (1976) : Coronal
holes, solar wind streams, and recurrent geomagnetic disturbances :
1973 - 1976, Solar Physics, 49, 271.
A - 52
SHORT-TERM PREDICTIONS OF A SUDDEN GEOMAGNETIC IMPULSE VALUE
ON THE BASIS OF THE INTERPLANETARY DATA
S. A. Grib
LOIZMIRAN, 23, Line 2, V.O.
199053 Leningrad, USSR
A new method for the prediction of a sudden geomagnetic impulse
value and the sudden storm commencement impulse resulting from the
study of solar wind shock wave collision with the bow shock wave-
magnetosphere system is proposed. The interplanetary data for the
discontinuity are taken as initial. The calculation is done within
the limits of the theory of the splitting of arbitrary magneto-
hydrodynamic discontinuity. Satisfactory agreement between the
calculated and the observed value of the geomagnetic impulse during
SSC is obtained. The thermal anisotropy value may be used as the
perturbation index for the solar wind flow. The correlation be-
tween the mhd evaluations and "Prognoz" satellite data is shown.
INTRODUCTION
The propagation of shock waves through the interplanetary space has been
investigated by many authors (Hundhausen, 1972; Dryer, 1975; Zastenker et al.,
1975). The tangential discontinuities often observed in the solar wind are
considered also in the context of a strong discontinuity model (Burlaga, 1971;
Grib, 1977). These discontinuities as they go through space effect the bow
shock wave (Brunei li and Grib, 1972; Volk and Auer, 197*0 and the magneto-
sphere of the Earth (Grib, 1973; Shen, 1973).
Ivanov (1965) and Dryer et al. (1967), in their studies of the solar wind
shock waves interaction with "the bow shock Si-magnetopause C " system, did
not consider the interplanetary magnetic field and the mobility of the magneto-
pause. Grib (1971, 1972, 1973) and Shen and Dryer (1971) showed that when the
solar wind wave collides with a bow shock two new shock waves, S3 and Si+, and a
contact surface are generated. They show that as the shock wave collides with
the maqnetopause, then the rarefaction wave, R, and the shock wave refracted
inside the magnetosphere appear simultaneously.
Vblk and Auer (197*0 obtained results identical to those of Grib (1971)
and Brunelli and Grib (1971); i.e., that the interaction of the tangential
discontinuity T (its proton concentration increases) with the shock wave re-
sults in two shock waves. But the tangential discontinuity T (which decreases
the proton concentration) produces the rarefaction wave: JJ> - .STR- These
A - 53
authors also indicated that the rarefaction wave reflected from the magneto-
pause appears to result from the influence of the nonstationary shock, wave.
V'olk and Auer used the gas dynamic relations, which are invalid in this case,
to change the gas pressure to the total pressure without considering the in-
tegral Tn(a) = J o 0 + axn~2)dx, where a = v^/a2 , the square of Alfven velocity
divided by the sonic velocity.
Neubauer ( 1975) considered the collision of a flat tangential discontinuity
with locally flat shock front limiting himself to the fast shock waves re-
fracted inside the magnetosheath. This author also indicated that the rare-
faction wave appears as a result of the interaction T£.
The purpose of this paper is to evaluate the sudden impulse Sl+ and the
impulse of the sudden geomagnetic storm ABSSC on the basis of the magnetohydro-
dynamic consideration of the solar wind shock wave collision with the bow
shock-magnetosphere system. In other words, we predict the magnitude of the
geomagnetic effect from the interplanetary data.
2. PREDICTION TECHNIQUE
The problem is to obtain the value of the abrupt change of the geomag-
netic field using experimental data that characterize the shock jump-like
change of the solar wind parameters. In other words, given the value d/dt(pu2)
and the derivative of total pressure (d/dt) (p) = dp/dt + (B/u7) (dB/dt) , where
d/dt = 3/3t + uV, in the solar wind we want to evaluate the geomagnetic im-
pulse, AB.
The nonstationary shock wave S2 propagating through the nonperturbed
flow (this region has the index "0" in Figure l) causes the abrupt increase of
all parameters charaterizi ng the flow condition: the concentration, the tem-
perature, the bulk velocity, u, and the intensity of the magnetic field. After
interacting with the bow shock wave Si the nonstationary magnetohydrodynamic
shock wave perturbs the flow inside the magnetosheath (indicated by index "1"
in Figure 1) and afterwards collides with the magnetopause, Cm, contracting
the magnetosphere of the Earth (region "m" in Figure l). The interaction of
Figure 1. Diagram of the interaction,
A - 54
the nonstat ionary solar wind shock wave with the bow shock is calculated from
the theory of the splitting of arbitrary discontinuity using the method de-
scribed by Brunelli and Grib (1972).
Given the ordinary Mach number, M2, for the running shock wave, we find
from the table of Brunelli and Grib (1972) the corresponding intensity (Mach
number) of the shock wave refracted inside the magnetosheath , M4 .
We assume that the interaction of the shock waves is regular, and that
for the current line in the magnetosheath, the equation of Bernoulli is valid:
u2/2 + i + B2/p + (vm/pu2)(curl B x B)u = const. (1)
where u is the bulk velocity, i is the enthalpy, B is the magnetic induction,
vm is the magnetic viscosity, and p is the density.
From the change of concentration at the shock front, we obtain the in-
crease of pressure from the mhd adiabate of Hugoniout:
p/p0 = {(hn - 1) + (Ya0/2)(n - l)3)/(h - n) (2)
Here, a = v^2/a2 = B02//tTrpoao , n = n/ng, ag is the sonic speed in the non-
perturbed region, h = (y + l)/(y " 0, Y is the politropic exponent, and n
is the concentration.
Taking the value of the pressure close to the stagnation point of the
magnetosphere calculated from the generalized equation of Bernoulli (1), we
obtain the change of pressure in the stagnation point (Grib, 1973):
Aps = 1 + (1 - 1/ti)yM2/(1 + 1/Bo) (3)
where gg = 8ttpq/B2. The time of the shock wave passing through the magneto-
sheath may be evaluated from
At = Jodx/[uj(l - j) + aiMj (h)
where 5 is the thickness of the nonperturbed magnetosheath, ui is the flow
velocity immediately after the shock front, and a\ is the sonic speed in this
reg ion.
From Aps we evaluate the change of geomagnetic intensity by the empirical
formula of Siscoe et al. (1968):
ABSSC = k (/p7 - /p^") (5)
in which k = 1 .35 x 105.
At the same time, Aps may be diminished as a result of the rarefaction
wave being reflected from the magnetosphere (Grib, 1972). For this case, the
changes in the velocity components are:
Au =
»x =+ (vA/yp02) / (p/p0)q±dp
Au =+ Xx sign (B /B ) (6)
y ± 3 y x
X± - (v^YPo"2) !?pi (p/po)"(Y+l)/2Y [(1 - q±)/(l " pq±)]^dp
Here the upper sign before the value corresponds to the waves which are
going to the right, and the lower sign to the waves going to the left. In the
lower index, the plus sign corresponds to a fast wave (R+) and the minus sign
to a slow wave, and q+ = a+2/ao2. Here a+ is the fast magnetosonic speed and
a_ is the slow speed.-
The sharp increase of the magnetic field intensity inside the magneto-
sphere may be found also from the generalized law of Crussard-Landau for the
A - 55
refracted shock wave which was obtained by Grib (1968, 1975):
(B/Bm)2 = 1 + [(B0/Bm)2 - 1][(1 + 2 vAm/3Aix0)(x/x0 + 2vAm/3AlXo)]^ (7)
where Bo = B| _ , Bm is the intensity of the geomagnetic field before the
front, Fi(C) = Ai£ + B is the shock wave profile, and £ = x - (u + v^)t. This
law may be used for determining the wave going from the magnetopause to the
plasmasphere. But beyond this the task is more complicated and the shock wave
degenerates to magnetohydrodynamic waves.
3. EXAMPLE
Let us take for an example the sudden commencement of the geomagnetic
storm of 15-16 February 1 967- At that time two satellites, Vela 3 and
Expl.-33, were in the free flow of the solar wind outside the magnetosphere.
The SSC was registered on the ground at 23h/t8m UT, February 15, 1967-
The satellite Expl.-33 registered the arrival of the shock wave four minutes
later. This testifies to the inclination of the shock front. On the shock
front, an abrupt change of the solar wind parameters was observed: the temper-
ature increased from 2.1 x 1014 to 12.7 x lO1^ and the bulk velocity from 271
to 388 kms"1 . These data are from Hirshberg and Colburn ( 1 969) and Hundhausen
(1970). (See Figure 2.)
Let us consider the interaction of the nonstationary shock wave of the
solar wind with the bow shock determined by the theory of the splitting of
arbitrary discontinuity as it has been described. For the moving shock wave
we have the Mach number, M2 -6-9and from examination of the shock wave colli-
660
580
VELOCITY, 500 -
km /sec 420
340
260
40
30
gamma 2°
10
0
.20 r
4 V- A
VELA 3A
T SHOCK
/y
EXPLORER 33
ARC MAGNETOMETE
a/P
.10 -
o *- **-
22 0
£
VELA 3A
0 a/P>.IO
j— ~i
2 4
14
FEB 15, 1967
Figure 2.
6 8 10 12
FEB 16, 1967
TIME, UT, hr
The solar wind parameters at the shock front.
A - 56
sion with the bow shock (Brunei 1 i and Grib, 1972) we have for the shock wave
refracted inside the magnetosheath , M^ - 1.9 for B0 = 3-5y (Bo is the inter-
planetary magnetic field).
Further we obtain the changes in the pressure in the magnetopause from
equation (3) and ABSCC - 30y from equation (5). This is the average value for
the midlatitude region. At the same time the observed increase of the H-
component at the San Juan observatory on February 15, 1967, was 38y ; and at
other observatories it varied from 35 to hS y . The observed value is higher
than the calculated one because we assumed a frontal collision but, in reality,
it was an oblique one, which causes a smaller decrease in the wave intensity.
In Figure 3, we see explicitly the smooth decrease of the geomagnetic
field intensity after the rapid increase. This decrease may be connected with
secondary wave interactions inside the magnetosheath (Grib, 1973).
If we take into consideration the oblique component of the interplanetary
field for the oblique shock waves, we have, in addition, slow shock waves and
slow rarefaction waves. But it is easy to show that for the typical inter-
planetary conditions their intensity is small in comparison with the fast
waves appearing in both the normal and oblique cases.
Let us apply this method to the August 1972 events. For the SSC of August
the fourth (0119 UT) we have (Dryer et al., 1976): M2 ■ 17.3, 3 = 0.16, the
ratio of gas pressure to magnetic. In this case, the calculated AB = 35y •
At the same time, AB at Moscow is 2% and at Leningrad, Ab = 26y.
For the August 8 event (235^ UT) , we have M2 = 10.3 and 3 = 0.24. Then
the calculated AB is 30Y and the observed AB is 48Y for Moscow and hU for
Leningrad.
CctH-OtCyotH, 15-16.H. 1967
UT
far
23.40
ryctM, tf-16.Il. 1967
Figure 3. The continuous magnetograms for the SSC on February 15, 1967:
San Juan (above), Guam (below).
A - 57
We know that the solar wind flow has thermal anisotropy considering the
direction of the magnetic field: T„ ^ Tx. From the method described by Grib
(1976) it is possible to find the change of concentration on the shock front,
x = n/ng , dependent on the field change, k = By/B for the given value of the
nonperturbed flow anisotropy X = (T(, - T±) / (B2/k-n] . The change of plasma con-
centration may differ significantly from the field change at the front (Grib,
1976). Meanwhile, from the laws of conservation, it is determined that the
degree of anisotropy is increasing after the shock wave front.
From the data of the Prognoz and Prognoz 1 satellites (Bloch et al., 1975)
on May 9, 1972, we see that on the shock front k = 1.96, x = O.kk; on August 8,
k = 1.3, x = O.65. All these values for X > 0 satisfy the formulae given by
Grib (1976).
SUMMARY
The proposed method may predict the magnitude of the geomagnetic impulse
on the basis of the interplanetary data. For the present level of the data
the error of calculation is rather satisfactory.
With this method it is possible to predict the magnitude of the geomag-
netic impulse both some minutes and some hours before the event—depend i ng
on the distance of the space vehicle from the Earth. The data on radio bursts
may be used to determine the shock wave velocity close to the sun.
The thermal anisotropy parameter X may serve as the characteristic of the
space perturbation degree.
The author would like to acknowledge Professor V. A. Troitskaya for useful
comments.
REFERENCES
Bloch, G. M., G. N. Zastenker, B. M. Kuzhevski i , S. B. Likin, N. F. Pisarenko,
I. A. Savenko, and V. A. Stiazhkin (1975):° The intensity bursts for the
low energetic charged particles connected with interplanetary shock waves.
Space Res. , 13:695.
Brunelli, B. E., S. A. Grib (1972): On the interaction of solar wind shock
waves with the magnetosphere of the Earth. In: Research in geomagnetism,
aeronomy and the physics of the sun, 23:369. English transl.: NASA
tech. transl. NAS 3-2481 (1973).
Burlaga, L. F. (1971): Hydromagnetic waves and discontinuities in the solar
wind. Space Sci . Rev. , 12:600.
Dryer, M. (1975): Interplanetary shock waves: Recent developments. Space Sci
Rev., 17:277.
Dryer, M., D. L. Merritt, and P. M. Aronson (] 967) : Interaction of plasma
cloud with the Earth's magnetosphere. J . Geophys. Res . , 72:2955.
A - 58
Dryer, M. , Z. K. Smith, R. S. Steinolfson, J. D. Mihalov, J. H. Wolfe, and
J.-K. Chao (1976): Interplanetary distrubances caused by the August 1972
solar flares as observed by Pioneer I.. J. Geophys. Res. , 81:4651.
Grib, S. A. ( 1 968) : The attenuation of flat shock waves in the transversal
magnetic field. Vestnik LGU, 1 : 77 -
Grib, S. A. (1971): On the interaction of the shock waves with the magneto-
sphere of the earth during geomagnetic storms with sudden commencement.
In: Program and Abstracts for the XV I UGG General Assembly. Moscow, 472.
Grib, S. A. (1972): The interaction of solar wind shock waves with the mag-
netosphere of the Earth. DAN BSSR, 16:493.
Grib, S. A. (1973): Some aspects of the interaction of solar wind shock waves
with the magnetosphere of the Earth. Geomagn. i. Aeronom. , 13:788.
Grib, S. A. (1975): On the shock wave propagation through the magnetospher ic
plasma. Geomagn. I ssledovania, 14:47.
Grib, S. A. (1976): The effect of anisotropic shock waves on the parameters
of interplanetary plasma. In: coll. The Materials of International Semi-
nar: Active Processes on the Sun and the Problem of Solar Neutrino.
Leningrad, 170.
Grib, S. A. (1977): Nonstat ionary interactions of the solar wind discontin-
uities with the bow shock-magnetosphere system. In: Symposi urn on the
Physics of the Magnetosphere. Irkutsk, 12.
Hirshberg, J., and D. S. Colburn (1969): Interplanetary field and geomagnetic
var iat ions--a unified view. Planet. Space Sci . , 17:1183.
Hundhausen, A. J. (1970): Solar wind properties and the state of the magneto-
sphere. Ann. Geophys. , 26:427.
Hundhausen, A. J. (1972): Coronal Expansion and Solar Wind. Springer-Verlag ,
New York.
Ivanov, K. G. (1965): On the interpretation of the observations of ssc of
geomagnetic storms in space. Geomagn. i. Aeronom., 5:471.
Neubauer, F. M. (1975): Nonlinear oblique interaction of interplanetary tan-
gential discontinuities with magnetogasdynamic shocks. J . Geophys. Res. ,
80:1213.
Shen Wen Wu, and M. Dryer (1972): Magnetohydrodynamic theory for the inter-
action of an interplanetary double-shock ensemble with the Earth's bow
shock. J. Geophys. Res., 77:4627.
Shen Wen Wu (1973): Interaction of interplanetary MHD shock waves with the
magnetopause. Astrophys. Space Sci., 24:51.
A - 59
Siscoe, G. L. , V. Formisano, and A. J. Lazarus (1968): Relation between geo-
magnetic SI and solar wind pressure changes—an experimental investigation,
J. Geophys. Res., 73 :4869-
Volk, H. J., and R.-D. Auer (197*0: Motions of bow shock induced by inter-,
planetary disturbances. J. Geophys. Res. , 79:^0.
Zastenker, G. N., V. V. Temny, C. d'Uston, and I. M. Bosqued (1978): The
form and energy of the shock waves from the solar flares of August 2, k,
and 7, 1972. J. Geophys. Res., 83: 1035.
A - 60
PREDICTION OF SUBSTORM ACTIVITY
TAKAO SAITO
Onagawa Magnetic Observatory and Geophysical Institute
Faculty of Sciences, Tohoku University
Sendai 980, JAPAN
A technique to predict magnitude of a substorm and orientation
to which the substorm disturbances expand is proposed by utilizing
the associated Pi2-type ULF wave. A background model for the pre-
diction technique is given. The longer-term predictions of sub-
storm activity is discussed in the last section by classifying the
term into several hours, one year, and eleven years.
1 . INTRODUCTION
One of the most fundamental and important disturbances of the earth's
magnetosphere is the substorm. All substorm activity is associated with
Pi2-type magnetic pulsations. This type of pulsation starts simultaneously
with onset of the expansion phase of "the substorm. In this sense, the onset
of every Pi2 and the onset of every substorm have a one-to-one relationship
(Saito, 1961; Saito et al., 1976a). Although Pi2 is numerically defined as a
type of pulsation with irregular waveform having the periods of 45-150 seconds
according to the 1963 Berkeley classification, Pi2 is observationally in a
period range from 30 to 300 seconds according to the physical classification
(Saito 1978a) . Substorm activity can be predicted by utilizing various
characteristics of Pi2 pulsation as will be explained in Sections 2, 3, and
4. A basic model for this Pi2-substorm relation will be given in Section 5.
The longer-term predictions of substorm activity will be discussed in Section
6.
2. PREDICTION OF SUBSTORM MAGNITUDE
Generally, substorm range maximizes about 30 minutes and recovers about
90 minutes after the onset of the substorm. The maximum range of a substorm
observed at a mid latitude station (Fredericksburg, Virginia, for example) is
called magnitude of the substorm. Magnitude M of a substorm is closely
related with the period T of the associated Pi2 as shown in Fig.lC.
This relation means that magnitude of a substorm can be predicted by
measuring the period of the initial two-three pulses of the associated Pi2
A - 61
PI2 ported,
«L 90 60 TO §0 90 100
tfC
110
140
100
ISO 200
|
•
•
• 20
4 ._
►
1
— A
& IS
V
1
.
%
-Co)
•
I
s 16
#K \
1
£
L*e_«
- IDJ-
1
1
1
63#
64*
100
K>
- ■ ■
_. f 1
(cl
I
I
,.,, i,
- K> »
•0 70 00 90 100 120
Pi2 period, sec
140 160 160 200
Fig.l Observed relation between Pi2 period and (a) tail
lobe energy (solid circles) , (b) geomagnetic
latitude of both maximum amplitude of Pi2 and the
instantaneous position of the auroral electrojet
(open circles) , and (c) magnitude of the associ-
ated substorm, respectively. The tail lobe energy
just before the onset of substorm is measured from
the magnetic field data obtained by Explorer 34.
The position of AE is inferred from the distribu-
tion of AZ and AH obtained at meridian chain sta-
tions. Since the M-T relation is dependent on the
phase of the solar cycle, an averaged relation
obtained from the data from 1957 to 1965 is
exhibited here.
62
pulsation. Hence, prediction of the magnitude can be executed within only
the initial two-three-minute duration for a substorm with M=100nT(Y), for
example, as shown in Fig.lC. Actually a substorm with M=17nT was observed
being associated with a Pi2 with T=80 sec that commenced at 21h20m LT at
Fredericksburg on December 16, 1961 (Saito and Matsushita, 1968). In this
sense the prediction on which we will discuss in the present paper will not
mean the prediction of substorm onset, but of substorm activity as is ex-
pressed in the title of this paper.
This kind of prediction is really useful to find a chance to launch a
rocket to aurora, to command a scientific observation to a polar -orbiting
satellite, to select a radio-propagation path for the transpolar telecommu-
nications, etc.
3. PREDICTION OF LATITUDE TO WHICH
SUBSTORM DISTURBANCES EXPAND
The amplitude of a Pi2 maximizes at the latitude where the instantaneous
main electrojet flows (Olson and Rostoker, 1975; Saito et al., 1976a;
Kuwashima, 1978; Oguti et al., 1978). The period T of the Pi2 is also relat-
ed to the latitude $ of the electrojet; T is longer for the larger $ as shown
in Fig. IB. Since the waveform of Pi2 becomes simplified in the lower lati-
tudes, T can be measured strictly at low-latitude stations. Therefore, $ can
be inferred from T of low-latitude Pi2. When $ is estimated to be small, we
can predict that the substorm which is now expanding will develop further
from $ to the higher latitudes, since the larger substorm makes generally a
prominent poleward expansion from the lower latitudes. Actually the latitude
$ was 65° geomagnetic latitude when a substorm was observed to start together
with a Pi2 with T=60sec at 21h30m UT on August 26, 1970 (Saito, et al. 1976a),
4. PREDECTION OF LONGITUDES TO WHICH
SUBSTORM DISTURBANCES DEVELOP
Magnetic disturbances during substorms are expressed by systematic
hodographs on the horizontal plane (Fukushima, 1953) . Hodographs of the
initial kick of Pi2-type magnetic disturbances are also governed by a system-
atic rule: initial kicks at stations in the northern hemisphere orient
statistically toward the convergent point on the northern auroral oval on the
midnight meridian (Saito, 1961; Rostoker, 1967; Saito and Matsushita, 1968).
Oguti et al. (1978) confirmed by using the observed data of sequential Pi2-
substorm events that this convergent point coincides with the substorm
ignition region to which auroral particles precipitate initially. Then activ-
ity of the substorm develop from this region toward both longitudes via
westward travelling surges and eastward travelling loops (Kisabeth and
Rostoker, 1973; Fig. 15 of Saito, 1974).
In actual cases the convergent point, namely the ignition region, is
sometimes situated far from the averaged midnight auroral oval (Fig. 4 of
Saito, 1961) . This conclusion that had been derived in 1961 was confirmed
afterwards by satellite auroral photographs, according to which the substorm
ignition region that is identified by an initial auroral brightening was also
frequently far from the midnight meridian (for example, see Figs. 4c and 4e in
Snyder et al . , 1974) .
A - 63
Hence, we can locate the longitude of the substorm ignition region (and
can predict the longitudes to which the substorm disturbances develop) by
using the associated Pi2 disturbance at a low-latitude station, if the orien-
tation of the initial kick of the Pi2 is combined with $ as obtained in the
previous section (Saito et al. , 1976a). Triangulation of initial kicks of a
Pi2 event observed simultaneously at many well-distributed stations promises i.
more precise locating of the ignition region (Saito, 1961) .
Actually the geomagnetic longitude A of the convergent point was about
280° for a substorm event that commenced at llh35.5m UT on August 29, 1957
(Kato et al. , 1962) .
5. BASIC MODEL FOR THE
PREDICTION THCHNIQUE
Various Pi2 models have been proposed by various researchers (Doobov and
Mainstone, 1973; Olson and Rostoker, 1977; Nishida, 1979; and others), but the
basic model which will be used here is the one by Saito et al. (1976a) that
Pi2 is due to a damped -type standing Alfven wave on the field lines anchored
in the auroral oval in the midnight sector. In this model the Alfven wave is
considered to be excited by the abrupt formation of the X-tvpe neutral line in
the magnetotail (Sakurai et al. , 1976) . In case when a large magnetic energy
is stored in the magnetotail, the radius of the auroral oval (namely, of the
polar cap) becomes large. Hence, if the large amount of energy is suddenly
released by the formation of the X-type neutral line, a substorm with large
magnitude commences associating with a poleward expansion from the low-
latitude auroral oval. In this case the period of the standing Alfven wave is
short, since the path-field line is short and the magnetic fields along the
field line are intense. The M-T relation as described in Section 2 and the $ -
T relation in Section 3 are interpreted in this way by this model. As for the
more comprehensive description on this Pi2 model, the reader may refer to
Saito et al. (1976a) or Kuwashima et al., (I960).
The convergent characteristic in the distribution of the initial kick of
the Pi2-type magnetic fluctuations (see Section 3 andA) is interpreted as due
to the repulsion forces among the field-aligned currents that are suddenly
intensified in association with the onset of the substorm (Saito, 1977).
6. LONG-TERM PREDICTIONS
OF SUBSTORM ACTIVITY
In the previous sections a technique to predict the substorm activity
before the activity reaches its maximum was described. Then let us discuss on
long-t^i-m predictions of substorm activity before its onset classifying the
term into various time lengths.
In the first place let us consider the prediction several hours before
substorm onset. When the orientation of the interplanetary magnetic field
(IMF) is southward, the solar wind energy is stored more in the magnetotail
via the reconnection between IMF and MMF (magnetospheric magnetic field) on
the dayside magnetopause . Hence, when IMF turns from northward to southward,
we can expect that a substorm with large M will break within a few hours.
However, we cannot predict the precise duration from the southward turning to
the substorm onset (Saito et al., 1976b). In the case of southward IMF (Saito
A - 6^4
et al. 1980 ), prediction of s,ubstorm becomes much more difficult.
Next, let us consider a prediction of substorm activity within the coming
one year. A recurrent-type magnetic storm is regarded as an assembly of
substorm events modulated by the sector structure of IMF (Saito, 1972a).
According to the Russell-McPherron effect, IMF tends to be southward near
around April 5 and October 5 (Russell et al.,1973). Since the Russell-
McPherron model is a one-dimensional model, a more realistic two dimensional
model was proposed with the name of SEQSM model (Saito, 1972b) . Since the
axial effect is decisively observable on geomagnetic disturbances, this effect
is called the ARS effect, which becomes maxima at March 8 and September 8
because heliolatitude of the subearth point maximizes. Hence, the ARS-SEQSM
model derived from a combination of two effects was regarded as the cause of
the seasonal variation and the 27-day recurrent variation of magnetic activi-
ty. We can expect from a combined model that magnetic activity becomes
maximum near around March 21 and September 21 as observed (Saito, 1972b).
According to the ARS-SEQSM model, the epoch of magnetically active days in
some solar rotation number can be fairly predicted by surveying the magnetic
activity data of one year ago (Saito, 1972b) .
As for the solar-cycle term prediction of recurrent-type magnetic (namely ,
substorm) activity, the dynamic auto-correction analysis of the past magnetic
activity indices (Fig. 2 of Saito, 1972b) may offer a useful information. The
figure shows that 27-day recurrent disturbances are statistically predicted
to occur from 3.5 years before to 0.5 years before sunspot minimum. This
interval is explained by the two-hemisphere model on the three dimensional
interplanetary magnetic structure (Saito, 1975). According to this model, a
warped neutral sheet of the helionagnetosphere turns over once every solar
cycle (Saito et al., 1978) and makes an apparent sector structure in the
160°
Fig
RELATIVE HELIOLONGITUDE
Stable antipodal relation of the two solar M-regions
that appeared simultaneously on the sun. The black
area in the northern hemisphere and that its anti-
podal position mean the M-regions from Ci and C9 indices
(cf. Fig. 1 of Saito, 1972b). Note the strikingly
stable antipodal relation has been held from 1890 (upper
panel) to 1974 (lower panel).
A - 65
sunspot declining-minimum years. Recurrent-type Sc and Si as observed (Saito,
1972c) is also expected from this two-hemisphere model (Saito, 1978b) . The
recurrent-type magnetic storm is closely related to the coronal-hole tongue
that is regarded to be the solar M-region. Saito (1978c) analyzed geomag-
netic Ci and C9 indices during almost one century and found a very stable
antipodal relation in the two M-regions that tend to appear simultaneously on
the sun. Fig. 2 shows that the antipodal relation of the two M-regions derived
from the Ci indices in 1890 is strikingly similar to that in 197 4 (Saito,
1978C).
Since the main purpose of the present paper is to propose a technique to
predict substorm activity by means of Pi2 , the reader may refer to the fol-
lowing references.
REFERENCES
Doobov,A.L. and J.S. Mainstone (197 3); Investigations of Pi2 micropulsations-
(I) Frequency spectra and polarization, Planet. Space Sci. , 21 : 721.
Fukushima,N. (1953) : Polar magnetic storms and geomagnetic bays. J. Fac . Sci.
Univ. Tokyo, Section II, 8:293.
Kato, Y. and T. Saito (1962) : Morphological study of geomagnetic pulsations.
J. Phys. Soc. Japan, 17:(Suppl. A-II)34.
Kisabeth, J.L. and G. Rostoker (1973) : Current loops in auroral loops and
surges inferred from ground-based magnetic observations. J. Geophys.
Res., 78:55 73.
Kuwashima, M. (1978) : Wave characteristics of magnetic Pi2 plusations in the
auroral region. Spectral and polarization studies. Memoirs of the
National Polar Research Institute. Series A. Aeronomy. 15:1.
Kuwashima, M. and T. Saito (1980) : Spectral characteristics of magnetic Pi2
pulsations in the auroral region and lower latitudes. Submitted to
J. Geophys. Res.
Nishida, A. (1979); Possible origin of transient dusk-to-dawn electric field in
the nightside magnetosphere , J. Geophys. Res., _84, 3409.
Oguti, T. , K. Hayashi, S. Kokubun, K. Tsuruda, T. Watanabe, and R. E. Horita
(1978) : Local auroral expansion and Pi2 . Abstracts for the 64th
Assembly of Japanese Society of Geomagnetism and Geoelectricity . 42 p.
Olson, J.V. and G. Rostoker (1975); Pi2 pulsations and the auroral electrojet
Planet. Space Sci. , 23:1129.
Olson, J.V. and G. Rostoker (197 7); Latitude variation of the spectral
components of auroral zone Pi2 , Planet Space Sci., 25:663.
A - 66
Rostoker, G. (1967); The polarization characteristics of Pi-2 micropulsations
and their relation to the determination of possible source mechanisms
for the production of nighttime impulsive micropulsation activity, Can.
J. Phys. , 45:1319.
Russell, C.T. and R.L. Mcpherron (L973) : Semiannual variation of geomagnetic
activity. J. Geophys. Res. 78:92.
Saito, T. (1961) : Oscillation of geomagnetic field with the progress of pt-
type pulsation. Sci. Rept. Tohoku Univ., Ser.5, Geophys., 13:53.
Saito, T. (1972a) : Structure of the interplanetary magnetic field and
occurrence of magnetospheric substorms Examination of hypotheses on
semiannual variation in substorm activity. Proc. 4th MagnetosphereSymp.
(on Magnetospheric Substorm), Publ. by Inst. Space Aeronaut. Sci.,
Univ. Tokyo, 7 2 pp.
Saito, T. (197 2b) : Recurrent magnetic storm in relation to the structure of
solar and interplanetary magntic fields. Rept. Ionos. Space Res.
Japan, 26:245.
Saito, T. (1972c) : Recurrent-type magnetic disturbances and prehistoric
solar magnetic field. Proc. IASY-IMS Symp . , Publ. by Inst. Space
Aeronaut. Sci., Univ. Tokyo, 167 pp.
Saito, T. (1974) : Examination of the Models for the Substorm-Associated
Magnetic pulsation, Ps6 . Sci. Rept. Tohoku Univ. Ser.5, Geophys., 22:35.
Saito, T. (1975) : Two-hemisphere model on the three-dimensional magnetic
structure of the interplanetary space, Sci. Rept. Tohoku Univ., Ser.5,
Geophys . , 23: 37 .
Saito, T. (197 7) : Study of mini-substorm as a suitable research themefturing
IMS, Proc. IMS Symp. held at ISAS, Tokyo Univ. on 14-16. July, 1977.
203 pp.
Saito, T. (1978a) : Long-period irregular magnetic pulsation, Pi3, Space Sci.
Rev. , 21:427.
Saito, T. (1978b) : Destruction of corotation shock by a solar flare. In:
Summary of Japanese IMS Observations presented at IMS Working Conferense,
Innsbruck, 46 pp.
Saito, T. (1978c) : Antipodal characteristics of solar M-regions that have
been observed for the past one century. Abstracts for the 63th Assembly
of Japanese Society of Geomagnetism and Geoelectricity . 70 pp.
Saito, T. and S. Matsushita (1968) : Solar cycle effects on geomagnetic Pi2
pulsations. J. Geophys. Res . , 73:267.
Saito, T., T. Sakurai and Y. Koyama (1976a) : Mechanism of association be-
tween Pi2 pulsation and magnetospheric substorm, J. Atmos. Terrestr.
Phys. , 38:1265.
A - 67
Saito, T. , K. Yumoto and Y. Koyama (1976b) : Magnetic pulsation Pi2 as a
sensitive indicator of magnetospheric substorm, Planet. Space Sci.,
24:1025.
Saito, T. , T. Sakurai and K. Yumoto (1978) : Tbe earth's paleomagnetosphere
as the third type of the planetary magnetosphere, Planet. Space Sci.,
26:413.
Saito, T., and T. Sakurai (1980) : N-type reconnection model to interpret
the mechanism of mini-substorm. Submitted to Planet. Space Sci.
Sakurai, T. and T. Saito (1976) : Magnetic pulsation Pi2 and substorm onset,
Planet. Space Sci., 24:573.
Snyder, A.L. , S.-I. Akasofu, and T.N.Davis (1974) : Auroral substorms
observed from above the north polar region by a satellite. J. Geophys.
Res., 79:1393.
A - 68
SHORT-TERM FORECASTING OF THE SUBSTORM
BREAKUP PHASE BASED ON GROUND MAGNETIC
OBSERVATIONS IN THE ZONE
OF MAGNETOSPHERIC CLEFT PROJECTION
V. V. Shelomentsev, V. M. Mishin, and T. I. Saifudinova
Siberian Institute of Terrestrial Magnetism,
Ionosphere and Radio Wave Propagation (SiblZMIR)
lrkutsk-33, P. Box k, USSR
A new geomagnetic index, PE, is introduced, based on the
records of stations located within the zone of magnetospher i c
cleft projection ($ - 75-8l°). At the pre-breakup substorm
period the PE-index reflects the intensification of two current
modes in the polar cap: DP-2, associated with the enhancement
of large-scale magnetospheri c convection, and PEJ (a polar
electrojet), producing a high-latitude effect of the IMF Y-
component. This defines the applicability of the index for
short-term forecasting of the breakup phase. The estimates
obtained provide evidence of a high degree of forecasting
accuracy with the help of the adopted technique (-80-90% for
isolated substorms and >60% for substorms in a sequence
-2-3 hours prior to breakup onset).
1. INTRODUCTION
A geomagnetic substorm is a complex phenomenon, accompanied by magnetic
field reconfiguration, formation and decay of plasma regions, and other large-
scale magnetospher ic processes, resulting in the release of considerable
energy (~1021-1022 erg) in the low ionosphere. This energy creates strong
ionospheric disturbances that often cause interference in normal operation
of radio communication lines, power lines, and other communication means. In
addition, there is some evidence that geomagnetic disturbances are closely
connected with the Earth's climatic conditions and its biosphere.
The above circumstances demonstrate the importance of improving substorm
forecasting techniques. Since the most remarkable substorm signatures are
detected during the breakup phase, the forecasting should, obviously, be based
on the discovery of specific changes in magnetospher ic and/or ionospheric
parameters during the prebreakup period (i.e., during the so-called "growth
phase").
The present paper describes the results of the development of the short-
term forecasting technique for a substorm breakup phase, inferred from ground
magnetic observations in the zone of magnetospher i c cleft projections
(♦-75-81°).
A - 69
2. GROUND SIGNATURES OF THE GROWTH PHASE OF THE MAGNETIC SUBSTORM
One is faced with some difficulties when selecting the ground substorm
signatures, especially at the prebreakup period. This is due, in many re-
spects, to the fact that a modern network of magnetic observatories is extreme-
ly sparse and nonuniform, particularly at high latitudes where the disturban-
ces, generated during substorms, are most intense. Thus, the use of data
from auroral (AE-indices) and midlatitude stations to define the beginning of
the breakup phase and other substorm characteristics often results in ambi-
guity due to discreteness and multiplicity of "elementary" breakups, forming
a single substorm (Clauer and McPherron, 197^; Sergeev, 197^; Vorobjev and
Rezhenov, 1975; Wiens and Rostoker, 1975). This leads to contradictory inter-
pretation of the growth phase and even to rejection of its existence and is a
subject of considerable controversy (see, e.g., Akasofu and Snyder, 1972;
Vasyliunas and Wolf, 1973; McPherron, 1972*) .
At the same time the use of polar cap data ($^75°) in the analysis of
substorms allows one to show that the most significant ground signatures of
the prebreakup period take place only at very high latitudes. Thus, in the
dayside polar cusp region ($~75-80°) there is activization and equatorward
motion of background aurorae (Starkov and Feldstein, 1967) and auroral par-
ticle precipitation regions (Burch, 1972). In the polar cap, DP-2 distur-
bances are developed (Nishida, 1971; lijima and Nagata, 1972). The occurrence
of DP-2 is of particular interest for forecasting because it can be detected
with the help of a special magnetic index PC, drawn by means of magnetograms
from stations near the pole ($>85°) (Fairfield, 19&7; lijima and Nagata, 1972)
According to the conclusions of Kuznetsov and Troshichev (1977), forecasting
the substorm breakup phase on the basis of the PC-index enables one to achieve
accuracy of about 70%.
Nevertheless, it should be noted that DP-2 is not a unique current mode,
characteristic of the prebreakup period in the polar region. The other impor-
tant element of this period is a polar (not auroral!) electrojet, PEJ ,
responsible for the high-latitude effect of the IMF Y-component (Mishinet al.,
1975; Sumaruk and Feldstein, 1975)- It is localized in the zone of a magne-
tospheric cleft projection ($~75-80°) and is most intense in its dayside sec-
tor, corresponding to the polar cusp projection. PEJ takes place at quiet
times too, but during substorms it is sharply intensified (as shown by Mishin
et al., 197^, 1977). Figure 1 shows the changes of equivalent current densi ty
in the midnoon sector versus substorm time (moment t=5 corresponds to the
breakup phase onset). On the average, the enhancement of current starts
"1-1.5 hours prior to the breakup, so that, together with DP-2, the intensi-
fication of PEJ may serve as an indicator of a substorm growth phase.
The additional evidence in favor of this conclusion is presented in
Figure 2 where the motion of disturbance onset in coordinates ($, t) is
shown. It is seen that the zone of the growth phase onset (moments t=1-2)
just corresponds to the magnetospher ic cleft projection region where a polar
electrojet is localized.
From all of the above facts, one can infer that the magnetic records from
stations of magnetospher ic cleft projection may serve as the basis for intro-
ducing a new index, suitable for short-term forecasting of a substorm breakup
phase.
A - 70
n-i3 Li
-i
/V'
0 30
tpa3a pocma \63pu6\ SoccmuiwSAeHue
growth bre<xk recovery
up
Figure 1. (a) Definition of substorm time
moments t by the idealized AL- index profile,
(b) Distribution of equivalent current density
(in amp/km) in coordinates "invariant latitude--
substorm time" for a midnoon sector (after Mi-
shin et al., 197*0- Data are obtained for a
"statistical" substorm, comprising a great
number of individual cases.
°. 4 _ 6 8
M&fO0>J>80 MI\w>j>50
3. A MAGNETOSPHERIC CLEFT INDEX, PE
3.1. A Technique for Index Drawing
To draw the index PE (abbreviated from "polar electrojet") the data of
six permanent magnetic observatories (three in the Northern and three in the
Southern Hemisphere, Table 1) were used for spring and fall of 1968. Equinox
seasons were selected because at these periods the solar illumination of both
polar caps is approximately equal and there is no need to introduce correc-
tions for seasonal variations.
Figure 2. A diagram of disturbance
onset movement in the polar region at
the substorm growth phase (moment t=
1-5 are determined on the left side of
Figure 1). A zone of the initial
disturbance is hatched (after Mishin
et al., 197*0- Data are obtained for
a "statistical" substorm, comprising
a great number of individual cases.
A - 71
Table 1. A network of stations for drawing PE-index.
coord i
i nates
Station
geog
raphic
corrected
geomagnetic
5
X
$
A
Godhavn
69.2
306. 5
77.6
43.3
Mi rny
-66.6
93.0
-76.6
127.4
Dumont D'Urvi
lie
-66.7
140.9
-80.1
228.7
Mould Bay
76.2
242.6
80.7
264.0
Baker Lake
64.3
264.0
75.1
320.4
Scott Base
-77.8
166.8
-80.5
323.4
It was found by experience that the best results for forecasting sub-
storms were obtained from the integral PE index, determined as a total of
disturbance amplitudes of the horizontal component at all stations used:
6
PE = I I H |-H | J (1)
i = l
where HQ is the background level of quiet days. The proposed technique for
index drawing is analogous to that for determining the AE-index (Davis and
Sugiura, I966) and differs from the latter only in smoothing of sharp peaks
in the magnetograms of some stations. In the present paper we have con-
fined ourselves only to computations of hourly indices because of simplicity
of original data processing, though the time resolution of the index may be
improved up to standard resolution of magnetograms, i.e., 2.5-minute values.
3-2. Physical Meaning of the Index
The PE index determined by equation (1) is integral not only in its
method of calculation but also in its physical sense, because it reflects the
dynamics of all current modes in the po^r cap, causing fluctuations of the
H component. During the most interesting (for forecasting) prebreakup period
the predominant contribution to PE is made by two main elements of the growth
phase current system—the one-vortex mode with electrojet PEJ and the two-
vortex mode DP-2. Their development is controlled, respectively, by a meri-
dional electric field (across a polar cusp) and by a "dawn-dusk" one (across
a polar cap). Therefore, to describe the physical meaning of the PE index,
its correlation with the theoretical measures of these electric fields should
be studied.
According to Gonzalez and Mozer (1973, 1974) the time variations of the
"dawn-dusk" field in the polar cap are well described by a model potential
A - 72
according to a theory of reconnection between interplanetary and geomagnetic
fields at the dayside magnetospher ic boundary. A formula for the potential
has the following form:
VBi (S-cosa)
(1+S^-2S cosa)^
(rel , un i t)
at S > cosa
at S < cosa
(2)
where V is solar wind velocity, Bj is the magnitude of the IMF, S ( = Bj/Bm) is a
ratio of interplanetary and geomagnetic field magnitudes at the lobe magneto-
pause, a is an angle between these fields (a=Tr/2 - tn_1£sM/| Ysm|), where Zsm
and Y$m are the vertical and azimuthal IMF components, respectively, in the
solar-magnetospher ic coordinates). For further computations we have adopted
S = 0.6, based on the results of a correlation analysis of the magnetic
activity with the IMF (Svalgaard, 1975; Shelomentsev, 1976).
Figure 3 illustrates an average picture for changes of $, AE and PE,
obtained by means of a superimposed epoch method for a sample involving 19
isolated substorms. Here and further a zero time (x=0) is consistent with
the beginning of a sharp AE-index increase, i.e., agrees with the definition
of the breakup phase onset (Akasofu; 1 968) . Note that this definition of x
differs from that adopted in Figures 1 and 2.
Figure 3- Normalized mean profiles
of changes of $ (dashes) , AE (sol id)
and PE (dot-and-dash) for isolated
substorms. x=0 corresponds to the
breakup phase onset. ["Isolated"
means a substorm, developing after
the quiet background (AE<100y) and
lasting for at least 6 hoursj
1
i A&U,
(%)
100
1 Y ■
V"\
80
ilr
\\
Npf
i
1
Jr
/
>AE
60f:
/!
81
//W
■ 1
//
/'/ 20-
„^* '
.^N / J
r , :^
r(«a
•5 -4 -J -2 -/ 1 2 J 4 hours
A - 73
Figure 3 shows a significant correlation between potential, $, and PE
index. At the same time certain differences are observed, particularly the
lack of coincidence of times of maxima. This is in agreement with the inte-
gral character of the PE index, involving the contribution not only of DP-2
whose measure is <*> but also of the electrojet PEJ. Unfortunately, the theore-
tical description of meridional electric fields in the ionosphere, controlling
the generation of PEJ, is not yet developed sufficiently to study the corre-
lation in more detail.
From Figure 3 it follows that the growth of $ and PE starts long before
the breakup onset (x=0)--in some cases as much as five hours before. A signi-
ficant increase of the PE index (-10% of the amplitude) is already observed
four hours prior to the breakup. This shows eivdence for the fact that one
can really detect the precursors of the substorm breakup phase with the help
of the PE index.
3-3- Forecasting the Breakup Phase by Means of the PE Index
Figures 4 and 5 give a representation ofprofiles $ , AE, and PE for
single substorms. Arrows show the beginnings of characteristic changes of
the PE index, precursors of the breakup phase.
3-3. 1. Isolated substorms
Typical examples of isolated substorms are given in Figure k. In each
individual case it is evident that the beginning of the changes of PE precedes
a breakup onset by several hours. Prebreakup time variations of PE are of
three types: (1) a smooth growth (Figure 4a); (2) oscillations with a quasi-
period -2-3 hours (Figure 4b); and (3) superposition of types 1 and 2
(Figure kc) . The characteristic values of PE corresponding to a substorm
(involving the growth phase) are hundreds of gammas. In fact, the stable
condition PE>l00y points in most cases to the fact that the breakup will start
in several hours.
3.3.2. Nonisolated substorms
Substorms often occur in a sequence rapidly affecting each other and
forming, when they are of sufficient numbers, the strongest worldwide distur-
bances—global magnetic storms. Examples of such successions are given in
Figure 5, in which the characteristic prebreakup changes of the PE index are
also observed. Almost every single breakup of a succession (AE burst) is
preceded by a PE burst. This means that observations in the magnetospheric
cleft zone can give information about the continuation or cessation of dis-
turbances that have begun in the auroral zone.
The accuracy of forecasting nonisolated substorms is less compared to
that for isolated substorms. Indeed, the observed changes of PE index before
an individual breakup of a succession is a superposition of a decreasing dis-
turbance, corresponding to the preceding substorm, and of an increasing one,
corresponding to a new substorm. Therefore, a moment of the PE growth onset
(a point of minimum), taken as a precursor of a new breakup, shifts toward
the moment of a new AE burst onset, as compared with the situation that
would be observed for substorms separated by a durable quiet interval.
A - Ik
a)
22 cenmnSpfi
4 oKmaSpo
' v I V
6 8 10 <2 H <6 UT
ZZ.IX
Figure k. Changes of $ (dashes), AE
(solid) and PE (dot-and-dash) for
single isolated substorms. Arrows
show the onsets of precursors in
PE index. Question marks show
possible but somewhat doubtful pre-
cursors .
10 12 I* 16 IB 20 UT
Z*i.X
? /0 12 IV 16 UT
1Z. Ill
IQceHTnadpsi 20ce\ wmsfipa
20 22
2 4 UT
19-ZO.tX
\k
iO cennifiopg
6 & to 12 ii^UJ
10, IK
SOKTHfltipf)
0 2^6 Z 10 Ul
s.x
tt Jiapma. /j\ ftuapma.
i i -i — i — i — i — i — f— i — i r ni.
19 21 2d \ 1 3 5 UT
12 2Q 22
2 ^UT
1-Z.tn
11 -v*. Ill
2SoKmnSp9
29oKmaSpfi
— i 1 1 r~
16 If 20 22
2 lUT
Z&-Z9.X
3.3.3- Accuracy of forecasting
Not being able to carry out the substorm prediction based on the PE
index in real-time, we have confined ourselves to the epignosis of the known
substorms during the time periods including 19 isolated and 21 nonisolated
substorms. To reveal the breakup precursors in the PE index we used the
criteria previously described (the character of time variations of PE and the
quantitative condition, PE>100y). The results are presented in Figure 6 where
the time dependence of the forecasting accuracy percentage preceding the
breakup onset t=0 is shown. These data yield a quantitative estimation of
the forecasting accuracy, achieved by introducing the PE index. The proposed
technique enables us to predict -80 percent of isolated substorms ~3 hours
A - 75
i 765r
2 ceHmeSpt
3ceHmi6pfi
-] ' r"-i 1 | 1 \ ; 1 1 r*=-
13 -itt.iii
6 S W 12 H
f4 /5 II 2fl 22
J./X
22 I Z 4 6 3 0 & HUT
&-9. IX
20cetims5p9
to 20 22
ZO.IX
8 10 12 » 16 18 20 22
Zi.lX
2 4 6 8 10 12 A 16 18 20 22 UfT
ZZ. IX
Figure 5- Changes in $ (dashes), AE (solid), and PE (dot-and-dash) for
substorm successions.
beforehand and almost all of them (95 percent) 1-2 hours prior to the
breakup. The forecasting accuracy of nonisolated substorms is lower due to
the reasons mentioned above. However, in this case a good enough accuracy
(>60 percent) may be achieved -2 hours beforehand. Note that the quoted
results should be considered only preliminary. To obtain more accurate
estimates it is necessary to expand the time period under consideration to
take into account the number of the "false alerts" and so on. Of course, the
final testing of the prediction method should be made in real-time.
A - 76
Figure 6. Accuracy of breakup phase
forecasting versus the time preceding
the breakup onset x=0 (in percentage)
Isolated
u30JiupoiaHHbie
(19)
mean
cpednsp.
(40)
nonisolated
Heu30tupoi)aHHbie.
+, * W)
-80
■60
■■41
■2D
h
ours
-4 -J -2 -/
k. CONCLUSION
In the present paper a new geomagnetic index PE is introduced, based on
magnetic records of the H-component at stations located in the zone of
magnetospheric cleft projection ($~75-8l°) . At the prebreakup substorm per iod
the changes of PE index reflect, mainly, the intensification of two current
modes in the polar cap: a two-vortex DP-2 system and a polar electrojet, PEJ.
This observation is supported by the results of the analysis both of single
cases and a "statistical" substorm (Mishin et al., 197**, 1977) as well as by
correlation of PE with the "dawn-dusk" electric field potential, computed by
means of the reconnection model of Gonzalez and Mozer (197*0.
The presence of the breakup precursors in the region of a magnetospheric
cleft, revealed with the help of the PE index, gives evidence in favor of the
substorm growth phase existence. The signatures of the growth phase are
observed both for single (isolated) substorms and for those forming a succes-
sion. Note that in some cases the disturbances of the PE index begin k-S
hours prior to the breakup onset that exceeds mean known duration of the
growth phase (-1-2 hours). In such cases we deal either with the very durable
growth phase or with specific events in the magnetospheric cleft zone,
reflecting, probably, the variations of solar wind parameters (particularly
IMF), overtaking the substorm development. Finally, there are few cases when
it is difficult (or impossible) to select the precursors with the help of the
PE index. It is possible that a certain negative role is played here by the
sparseness and nonuni formi ty of the network of magnetic observatories (shown
in Table 1).
The approbation of PE index for short-term forecasting of the substorm
A - 77
breakup phase shows that a high degree of accuracy may be achieved. There-
fore, a new index may be recommended for various applied problems, including
forecasting of the breakup phase, together with the PC index and other mea-
sures of the substorm growth phase signatures.
Subsequent improvement of the proposed index is probably possible by the
accounting of not only amplitudes but also changeability of magnetic varia-
tions in the polar region. According to Kuznetsov and Troshichev (1977) a
similar modi ficat ion, approbed with PC index, results in significant improve-
ment of forecasting data. It is necessary also to make the analysis during
the solstice seasons to avoid introducing corrections for seasonal variations
when computing the PE index. In addition, the problems of further improve-
ment of the forecasting technique yield the necessity to expand the network
of magnetospheric cleft stations in Arctic and Antarctic.
Acknowledgment
The authors express their thanks to A. D. Bazarzhapov, V. Kh . Kompanets
and N. Ja. Naidenova for their help in this work.
REFERENCES
Akasofu, S.-l. (I968): Polar and Magnetospheric Substorms. D. Reidel Pub.
Co., Dordrecht, Holland.
Akasofu, S.-l., and A. L. Snyder (1972): Comments on the growth phase of
magnetospheric substorms. J . Geophys . Res . , Vol. 77, p- 6275.
Burch, J. L. (1972): Precipitation of low-energy electrons at high latitudes:
Effects of IMF and dipole tilt angle. J . Geophys. Res. , Vol. 77,
p. 6696.
Clauer, C. R. , and R. L. McPherron (197*0: Variability of midlatitude magnet-
ic parameters used to characterize magnetospheric substorms. J. Geophys.
Res., Vol . 79, p. 2898.
Davis, T. N., and M. Sugiura (1966): Auroral electrojet activity index AE
and its universal time variation. J . Geophys . Res . , Vol. 71, p. 785-
Fairfield, D. H. (I967): Polar magnetic disturbances and the IMF. Space
Res., Vol . 8, p. 107.
Gonzalez, W. D., and F. S. Mozer (1973): Response of polar cap convection
to the IMF. J. Geophys. Res., Vol. 78, p. 678^.
Gonzalez, W. D., and F. S. Mozer (197*0: A quantitative model for potential
resulting from reconnection with an arbitrary IMF. J . Geophys . Res. ,
Vol. 79, p. /»186.
lijima, T., and T. Nagata (1972): Signatures for substorm development of the
growth phase and expansion phase. Planet. Space Scl . , Vol. 20, p. 1095.
A - 78
Kuznetsov, B. M., and 0. A. Troshichev (1977): On the nature of polar cap
magnetic activity during undisturbed periods. Planet. Space Sci., p. 15.
McPherron, R. L. (197*0: Current status of the growth phase controversy.
EOS Trans, of AGU, Vol. 55, p. 99*+.
Mishin, V. M., A. D. Bazarzhapov, T. I. Saifudinova, V. D. Urbanovich and
V. V. Shelomentsev (197*0: Development of magnetic substorms. I.
Issled. po Geomagn., Aeron. i Flzike Solntsa, issue 30, Moscow,
Nauka, p. 107 ( i n Russian) .
Mishin, V. M., A. D. Bazarzhapov, M. I. Matveev, T. I. Saifudinova and
V. V. Shelomentsev (1975): Polar electrojet. I ssl ed. po Geomagn . ,
Aeron. i Fizike Solntsa, issue 36, Moscow, Nauka"^ p~. ^ ( i n Russ ian) .
Mishin, V. M., A. D. Bazarzhapov, T. I. Saifudinova, V. V. Shelomentsev and
G. B. Shpynev (1977): Development of magnetic substorms. II. I ss 1 ed.
po Geomagn., Aeron. i Fizike Solntsa, issue *t3, Moscow, Nauka, p. 23
( in Russ ian) •
Nishida, A. (1971): DP-2 and polar substorm. Planet. Space Sci . , Vol. 19,
p. 205-
Sergeev, V. A. (197**): On longitudinal localization of the substorm active
region. Planet . Space Sci . , Vol. 22, p. 13**1.
Shelomentsev, V. V. (1976): On functional dependence of planetary magnetic
activity upon "viscous friction" and IMF components. Issled. po
Geomagn., Aeron. i Fizike Solntsa, issue 39, Moscow, Nauka, p. 122
( in Russian) .
Starkov, G. V., and Y. I. Feldstein (1967): A scheme of elementary distur-
bance in aurorae at the day side of the Earth. Geomagnetism & Aeronomy,
Vol. 7, p. 367 (in Russian).
Sumaruk, P. V., and Y. I. Feldstein (1975): Magnetic field variations in
the polar cap. In: Substorms and Disturbances in the Magnetosphere,
Leningrad, Nauka, p. 170 ( in Russ ian) .
Svalgaard, L. (1975): On the cause of geomagnetic activity, SUIPR Rept.
No. 6A6, Stanford Univ., California.
Vasyliunas, V. M., and R. A. Wolf (1973): Magnetospher ic substorms: some
problems and controversies. Rev. Geophys. Space Phys., Vol. 11, p. 181.
Vorobjev, V. G., and B. V. Rezhenov (1975): Jump-like westward motion of the
region of auroral substorm localization at the impulse magnetic field
change. In: Substorms and Disturbances in the Magnetosphere, Leningrad,
Nauka, p. 103 (in Russian).
Wiens, R. , and G. Rostoker (1975): Characteristics of the development of the
westward electrojet during the expansive phase of magnetospher i c sub-
storms. J. Geophys. Res., Vol. 80 , p. 2109.
A - 79
DEVELOPMENT OF DISTURBANCES AFTER SC AND SI
I . N. Men ' shut ina
Polar Geophysical Institute
Apatity, USSR
The difference between SI and SC is assumed to be determined
by the states of the magnetosphere and solar wind at the time of
the appearance of discontinuities and shock waves to the magneto-
sphere. The behavior of solar wind parameters (B, Bx, By, Bz, V,
and den) and the state of the magnetosphere both before and after
SC and SI are studied to find the parameters that are important
for SC and SI. The determination of such parameters allows pre-
diction of the disturbances connected with solar wind discontin-
uities and shock waves since the SCs are accompanied by disturbances
the Sis are not.
1. INTRODUCTION
Two types of sudden changes of the geomagnetic field with large ampli-
tudes are known presently: sudden commencements (SC) and sudden impulses (Si).
[The sharp changes in the geomagnetic field with a small amplitude (A < l6y)
are termed sudden worldwide changes (Rigby and Mainstone, 1975)-] SC and SI
were originally determined by using the ground geomagnetic field observations.
The essential difference between them, taken as the basis for the determina-
tion, was the behavior of the magnetic field after the impulse: the impulses
followed by a magnetic stormi were called sudden commencements, the others were
sudden impulses. According to the 1AGA Bulletin, the SCs as a rule are im-
mediately followed by disturbances. These disturbances were observed by most
stations. The Sis are not accompanied by these disturbances at most stations.
Thus, the definitions of SC and SI are based on the different behaviors
of the geomagnetic field. However, there are many investigations where the
difference between SC and SI is not taken into account, for example Ondoh ' s
(1970) work considering the SC and SI amplitude distribution. Furthermore,
the cosmic noise absorption characteristics are shown to be the same for SCs
and Sis by Brown (I967) .
SCs and Sis cannot be connected with the principally different solar wind
phenomena. It has been shown that both SCs and Sis can be associated both
with shock waves and with discontinuities of solar wind (however, the prob-
ability is not the same) (Bur laga , 1975; Burlaga and Ogilvie, 1 969 ; Chao and
Lepping, 1971*; Gosling et al., 1967; Hirsberg et al . , 1970; Moldovanu, 1 97^ ;
and Nishida, I96A, 1975)- Since SCs and Sis are associated with the same
group of solar wind phenomena, the geoef f iciency of these phenomena, that is
the development of the disturbances immediately after the impulse and the de-
A - 80
velopment of the magnetic storm (and in this way the determination of SC and
SI) is determined by the state of the magnetosphere at the time of the dis-
continuities or shock wave and also by a number of parameters of solar wind
that influence the state of the magnetosphere. The determination of such
parameters allow prediction of the geoactivity associated with the solar wind
discontinuities, shock waves, and irregularities.
The other side of this problem concerns the triggering of substorms by
SC. Taking into account the results of the investigations considering the
SC-triggering problem (Akasofu et al., 1973; Burch, 1972, Jijima, 1973; Kawa-
saki et al., 1971; Kokubun, 1972; Kokubun et al., 1977; and Shieldge and
Siscoe, 1970), it is possible to find sufficient and necessary conditions for
triggering both substorms (accompanied by all its features) and other dis-
turbances. SC investigations can be useful for studying the connection be-
tween substorms, disturbances, and magnetic storms.
2. RESULTS
The principal factors determining the geoef f iciency of shock waves and
solar wind d iscontinui t ies. accord i ng to the results of the present investiga-
tion, are the interplanetary magnetic field; the velocity and number density
of the solar wind; the state of the magnetosphere characterized by Dst and AE
indices; and the angle between the interplanetary magnetic field and the di-
pole axis of the Earth.
Accordingly, both hourly average values for solar wind parameters pub-
lished by King (1977) and the hourly averaged magnitudes of the Dst and AE
indices were studied. The state of the solar wind one hour before the impulse
and for one hour during the impulse were studied. Changes in the above-men-
tioned parameters connected with the existence of shock waves and discontin-
uities were considered. The SC and SI data represented by the IAGA Bulletin
(I969) were used for investigation. For this period, graphs showing the be-
havior of the solar wind and magnetosphere before and after SC and SI, de-
pending on UT, were constructed (Figs. 1 and 2). There were no evident UT
dependencies of any parameter both for SC and SI. According to the figures
the behaviors of a number of parameters were different for SC and SI.
The principal statistical results of the graphs are given in Table 1,
which contains the median values of all the paVameters for one hour before SC
and SI and for the hour including SC and SI, the quarter values indicating
the value scatter. The changes of the parameters are also estimated: the
probability of change occurrence (in percent) and the values of changes are
g i ven.
As can be seen from Figures 1 and 2 and Table 1, the following features
are characteristic for SC (average values):
a. The magnitude of the interplanetary magnetic field changes substan-
tially. As a rule, B values increase during the hour including SC . The
probability of the increase is 85%. The change equals 2.8y.
b. The By component undergoes the largest change among components of
the interplanetary magnetic field. Though both an increase and decrease of
the By component are possible, the decrease is observed more often {65%).
However, the value of the change is larger at By increasing during the hour
of SC (ABy = 2.9y)- The median values of By are negative.
c. The Bx component changes are not essential. The Bx decrease and in-
crease probabilities due to SC are nearly equal. The median magnitudes before
A - 81
B«lO
Bx(0
+
II
7 -
6 -
ft
i t,
0 3 6 ) li IS II H It IT 1 3 6 9 12 15 IS 21 21 !/r
Bzfri
6 9 12 15 It 2( 2* W
41*
3 6 9 12 15 II 21 24 Iff 0 3 6 9 12 »5 B 21 21 1/r
Figure 1
Behavior of B, Bx, B , and Bz before and after SC and SI.
and after SC are positive and approximately the same. This sector of the in-
terplanetary magnetic field is unchanged, with the primary direction toward
the sun. However, SC does change the ratio of Bx to By.
d. The median magnitude of Bz is negative both before and after SC .
Bz both increases and decreases; however, the amplitude of the decrease is
larger than that of the increase and is equal to -2.5y»
e. The median velocity is ^00 km/sec before SC, corresponding to the
quiet solar wind velocity. The probability that there is no change in velo-
city is 5k%\ that the velocity increases is k$%. The median velocity after
SC is equal to hkO km/sec.
f. The number density either decreases or stays constant. The median
values are 3 cm-3 and 3-8 cm-3 before and after SC, respectively.
g. Before SC the median D t value is negative (-2y). As a rule, the
Dst increases during SC. The average Dst change is 7-6y, with Ds^ becoming
82
sc
If xm/itc
V Km/stt
AE,r
1500
woo
HUO
SOg
1100
woo
BOO
too
700
,nc
500
WO
300
A£/
-U-.
/5O0
1100
(300
(200
1100
IO00
000
100
TOO
too
500
m
T +
200
+ t+ +
fi*
_i > »
0 3 6 9 12 15 It 21 21 UT 0 i 6 9 (2 15 (J 2( 21 l/r
»
. M,1
0 i 6 9 12 15 IS 21 21 UT
D5t;>)
0 3 6 9 12 15 II II 21 UT
Dstfr)
1- t
II
! II
•(0
-20
•30
-IP
-50 "
-60
-70
den(cms)
1295
de/i (cm '
1
t +
|U+
iv*
+ T
i 1
! i U+*j
+
++ +
»+ it
0 3 6 9 12 IS IS 21 It Ul
0 i 6 9 12 15 It 21 21 UT
0 }( 9 12 IS IS 21 21 UT
0 3 6 9 12 IS IS 21 21 UT
Figure 2. Behavior of AE, Dst, V, and den before and after SC and SI.
positive. In this case either a large magnetospher ic compression or DR cur-
rent disappearance can occur. Sometimes Dst decreases; however, the de-
creasing value is ^.3y- That may correspond to simultaneous development of
the two processes: increasing DR current and magnetospheric compression.
The first process is more intensive.
h. The auroral zone disturbance is not large. The median AE index is
equal to l20y. The change of disturbances due to SC is not considerable.
AE is 150 y. The AE index can increase and decrease after SC.
The following features are typical for sudden impulses:
a. The median value of IMF increases after SI, probably due to the in-
crease of the B field after SI. Increase and decrease values are approxi-
mately equal .
b. By is negative before as well as after SI.
c. Bx can either increase or decrease after SI, with the decrease
value of Bx exceeding the increase value after SI. The sector remains un-
changed.
d. The median Bz values are positive. B2 more often increases (55%)
A - 83
Table 1. Statistical Results.
Considered parameters SC S I
Bx med + 0.2 Y 0.5 y
Bx quart + 2.7 Y; "2.0 y 2.6 Y; -2.2 Y
Bx med (.) 0.5 y 0.0 y
Bx quart (.) 3-6 y; -1.5 y 2-5 y; "3-1 y
ABx < 0 -1 .45 y -2.25 y
occurrence probability of ABX < 0 50% 50%
ABx > 0 1 .43 y 1 -79 y
occurrence probability of ABx > 0 50% 50%
By med + -0.5 y "0.5 y
By quart + 3-1 yl -3-9 y 4.1 YJ "3-3 y
By med (.) -l.Oy -1.9 y
By quart (.) 2.7 y', "5-3 y 3-9 yJ _i*-9 Y
ABy < 0 -2.13 Y "3- 1 Y
occurrence probabi 1 i ty. of ABy < 0 65% 49%
ABy > 0 2.90 y 3-05 y
occurrence probability of ABy > 0 35% 51%
Bz med + -0.5 y 0.6 y
Bz quart + 2.5 y; -1.9 y 1-7 yl -!•*» Y
Bz med (.) -0.3 Y l.Oy
Bz quart (.) 2.7 yJ "2.5 y 3-4 Y; -3-2 Y
ABz < 0 -2.5 y -3.2 Y
occurrence probability of ABz < 0 45% 37%
ABz > 0 1 .6 Y 3-4 Y
occurrence probability of ABz > 0 55% 55%
Bmed + 6.0 y 7-2 y
Bquart + 8.2 Y; 4.8 Y 10.6 Y; 5-2 Y
Bmed (..) 8.2 Y 7-6 Y
Bquart (.) 11.6 Y; 5-8 Y 9-6 Y; 6.0 Y
AB < 0 -1 .5 y -2.2 Y
occurrence probability of AB < 0 7% 41%
AB > 0 2.8 Y 2.0 Y
occurrence probability of AB > 0 85% 54%
Vmed + 400 km/sec 465 km/sec
Vquart + 460; 365 km/sec 570; 400 km/sec
Vmed (.) 440 km/sec 480 km/sec
Vquart (.) 490; 390 km/sec 560; 415 km/sec
AV < 0 -40 km/sec -12 km/sec
occurrence probability of AV < 0 2% 18%
AV > 0 35 km/sec 29 km/sec
occurrence probability of AV > 0 43% 32%
occurrence probability of AV ■ 0 54% 50%
A - 84
Table 1. Statistical Resul ts--cont i nued,
Considered parameters
den med +
den quart +
den med ( . )
den q u a r t ( . )
Aden < 0
occurrence probability of Aden < 0
Aden > 0
occurrence probability of Aden > 0
occurrence probability of Aden = 0
Dst med +
Dst quart +
Dst med (.)
Dst quart (.)
ADst < 0
occurrence probability of ADst < 0
ADst > 0
occurrence probability of ADst > 0
occurrence probability of ADst = 0
AE med +
AE quart +
AE med (.)
AE quart (.)
AAE < 0
occurrence probability of AAE < 0
AAE > 0
occurrence probability of AAE > 0
occurrence probability of AAE = 0
S£
11
3.0 cm"3
5.0 cm"3
h.3; 0.0 cm-3
7.2; 0 cm"3
3.8 cm-3
5.0 cm"3
7. 1 ; 0.0 cm"3
9.0; 0 cm"3
-0.2 cm-3
-^.0 cm"3
2%
33%
2.6 cm"3
3.3 cm"3
k3%
2k%
h3%
k2%
-2 Y
2 Y
7 y; "12 Y
16 y; -20 y
*» Y
10 Y
13 y; (-3)y
21 Y; "27 Y
2^.3 Y
S-h Y
20%
3**%
7.6 Y
8.2 y
76%
55%
2%
11%
120 y
190 Y
270 Y; 50 y
290 y; 90 y
150 y
210 y
370 y; 70 Y
^70 y; loo y
Sh y
99-5 y
17%
**0%
128 y
132 Y
71%
55%
12%
5%
Notations used in Table 1:
x med + median value of x parameter one hour before SC (SI)
x quart + quarter value of x parameter one hour before SC (Si)
x med (.) median value of x parameter during an hour including SC (Si)
x quart (.) quarter value of x parameter during an hour including SC (Si)
Ax average change of x parameter
A - 85
than decreases after SI with the values of change in both cases being ap-
prox imately equal .
e. The changes in velocity are not essential. The velocity value be-
fore SI is ^65 km/sec, i.e., the solar wind is weakly disturbed. The velocity
either remains constant or increases.
f. The density does not change, but it is large (5 cm-3).
g. Dst is positive before SI, i.e., DR current is small or absent. Dst
more frequently increases due to SI, i.e., the magnetosphere is compressed.
When a small DR current exists before SI, it decreases still more due to SI.
However, one can observe the Dst decreasing. The decreasing value is con-
siderable and equal to -9-^Y- In this case appearance (or increasing) of
DR current is possible.
h. The AE index value is equal to 1 90y before SI and 2l0y after SI.
According to these obtained and formulated results, shown in Figures 1
and 2 and Table 1, the principal differences between the behaviors of the
average parameters for SC and SI consist of the following:
a. The interplanetary magnetic field preceding SI is more intensive.
The B value is equal to 7-2y, exceeding the B value for the quiet solar wind.
However, the change of interplanetary magnetic field is larger in the case of
SC.
b. The Bz component is negative before SC and positive before SI.
c. The Bx component increases after SC and decreases after SI. The Bx
value preceding SC is equal to the one preceding SI.
d. There is a sharp distinction in the behavior of the By component due
to SC and SI. By changes after SI but not after SC .
e. The solar wind velocity before SI exceeds the solar wind velocity
before SC . However, more considerable velocity changes are observed after
SC, analogous to B behavior.
f. The number density is larger for SI and its value is constant. Af-
ter SC the number density increases.
g. D5t is negative before SC, i.e., the DR current exists and the mag-
netsophere compression is not too large. Before SI, Dst is positive and DR
current is small or absent. As a rule Dst increases both after SC and after
SI.
Thus, before SI the solar wind is weakly disturbed and DR current is
either weak or absent. The changes of parameters are not considerable in the
case of SI, but the situation is opposite for SC : the parameter changes that
take place in the initially quiet solar wind have the largest value.
3. DISCUSSION AND SPECULATION
Individual cases show that there are deviations from the average in the
behavior of parameters; however, as a rule, one can observe variations of a
range of parameters, and the variations of one of them is compensated by the
variation of the others. Taking into account the correlation between the
solar wind parameters and the state of the magnetosphere and the cause-effect
connect ion, one can consider another parameter determined by a combination of
the above described parameters. The distance to the subsolar point (R0) and
its variation (AR0) may be taken as such a parameter, as the RQ is determined
by the state of the solar wind and its variation is proportional to the en-
ergy transmitted to the magnetosphere tail independently on the mechanism of
A - 86
transference (Aubry et al., 1970). Thus, the difference between SI and SC is
that for SI the transferred energy is less than for SC (i.e., AR0$q > AR0$|).
The estimations of RQ and R0 made for median parameter values according
to Shin and Konradi (1975) indicate that the above is true when SC develops
in quiet conditions and SI in weakly disturbed ones. This is the average
case in which a^o 1. ^E anc' ■* 's eclual to 0.6R^ for SI.
If sharper change of solar wind parameters is taken into account, cor-
responding to the change from the quiet conditions to disturbed ones, the
difference in AR0 for SC and SI increases and is about 3&E- It should be
noted that the approximate values of RQ and ARQ correspond to real ones, be-
cause Bz is positive for SI and its negative value for SC is small, so the
field line reconnection and the RQ change due to this process can be neglected
The existence of the considerable negative Bz component after SC provides
the continuous energy transference and makes disturbance development possible
during a longer period of time. It probably leads to the magnetic storm.
This is the average picture. Individual cases differ variously. For example,
one can observe SC when Bz > 0. The various individual cases may be explained
at least qualitatively in the frame of the following picture. The change of
the convection regime occurs due to the changes of the solar wind character-
istics including the total magnetic field, its heterogeneity and velocity,
density, and viscosity at the magnetospher ic boundary. It leads to the elec-
tric field directed from dawn to dusk. The existence of electric field re-
sults in the accumulation of energy in the magnetospher ic tail. Along with
this process the energy accumulation is controlled by the sign and magnitude
of the Bz component of IMF.
The existence of positive Bz leads to carrying away the magnetospher ic
plasma to the distant tail due to the plasma drift in perpendicular magnetic
and electric fields. The latter appears due to E = (-1/C)[B x V] and has the
opposite direction in comparison with the E field of the convection. Thus,
the condition Bz < 0 always provides the development of disturbance after SC
and SI, in agreement with the results of Jijima (1973), Kokubun (1972), and
Kokubun et al . (1977)- The development of disturbances when Bz > 0 depends
on intensity correlation of both processes considered above. The value and
the direction of the summarized electric field will determine both the pos-
sibility of development of disturbances and the magnetosphere distance at
which the region of maximum energy will be localized. One can suggest that
this region will be displaced at a large distance from the Earth (to higher
latitudes). The characteristics of these disturbances may differ from those
of the auroral substorm occurring at auroral latitudes. The displacement of
the disturbed region influences the AE index behavior but AE index changes
may not be substantial. Such behavior of AE can be observed in any cases of
SC and SI. It should be noted that when the activity region is displaced to
very high latitudes SC cannot be marked in the IAGA Bulletin because the
latitudinal distribution of the station is not uniform.
k. CONCLUSION
Preconditions and changes in solar wind parameters, which lead to an en-
ergy increase in the Earth's magnetopshere, are necessary for triggering dis-
turbances after SC and SI. On the average the preconditions and solar wind
changes for SC provide the energy increase due to convection strengthening,
which is not connected with the existence of negative Bz (the change of RQ
A - 87
is more than 1 R^) . The quiet solar wind and negative D . (DR current ex-
istence) before the impulse are essential in this case for convection
strengthen ing .
Before SI the solar wind is disturbed, Ds*. is either absent or small,
and Bz is positive. The change of parameters (Dst and solar wind param-
eter) provides a smaller ARQ than in the SC case. The average value of
ARQ is equal to 0.6 R^ and it is not sufficient for a critical energy in-
crease in the magnetosphere tail.
In certain cases there are deviations from the average values in the
investigated parameters (B, Bx, B , Bz, V, den, AE, Dst) . In these cases
the possibility of triggering is determined by the correlation between
the energy connected with the convection strengthening and that connected
with the Bz component. The values of the Rq, Bz, and V magnitudes de-
termines both the probability of triggering and the latitudes at which
the maximum disturbance will be observed [with Bz < 0 at the ARQ value,
estimated according to Shin and Konradi (1975), can be considered effect-
ive, not including the R change caused by the negative Bz existence].
One can observe the displacement of the active region to higher latitudes
when B2 is positive and ARq is large.
According to Boiler and Stolov (1970), and Russell and McPherron
(1973), at certain UT moments the significance of the B2 component can be
taken by By, expecially when there are considerable changes in the By
component. However, using data of one year, we did not find any UT
dependence for SC or SI.
If Bz > 0 for a long time after SI a magnetic storm is impossible
because there are no sources and the energy due to convection strength-
ening due to the impulse is depleted.
The obtained results may be used for the prediction of geomagnetic
activity after the impulses. The main points are estimations of the
solar wind state and Dst value (DR current existence) before impulse and
their changes, which permit a determination of R0 and ARQ (real or ef-
fective). The ratio of the R0, AR0 and Bz values determines the prob-
ability of a disturbance developing and the character of the disturbance
after the impulse: with Bz < 0 the substorm accompanied by all known
features is triggered; with Bz > 0 the character of the disturbance will
be determined by the convection strengthening. The intensity of both
disturbance types may be the same (Domingo, 1978).
REFERENCES
Akasofu, S. I., P. D. Perreault, F. Yasuhara, and C. I. Meng (1973):
Auroral substorms and interplanetary magnetic field. J. Geophys.
Res., 78:7^98-7508.
Aubry, M. F. , C. T. Russell, and M. G. Kivelson (1970): Inward motion
of the magnetopause before a substorm. J . Geophys . Res. , 75:7018-
7031.
Boiler, B. R. , and H. T. Stolov (1970): Kel vin-Helmhol tz instability
and the semiannual variation of geomagnetic activity. J. Geophys.
Res., 75:6073-6083.
A - 88
Brown, R. R. (1967): Auroral-zone electron precipitation accompanying
a sudden impulse in the geomagnetic field. J . Geophys . Res . , 72:
2448-2451.
Burch, J. L. (1972): Preconditions for the triggering of polar magnetic
substorms by storm sudden commencement. J . -Geophys . Res . , 77 : 5629-
5632.
Burlaga, L. F. (1975): Interplanetary streams and their interaction with
Earth. Space Sci . Rev. , 17:327-352.
Burlaga, L. F., and K. W. Ogilvie ( 1 969) : Causes of sudden commencements
and sudden impulses. J. Geophys. Res., 74:281 5~2825.
Chao, J. K. , and R. Lepping (197*0: A correlative study of SCs, inter-
planetary shocks and solar activity. J . Geophys . Res . , 79 '• 1799"1807-
Domingo, V. (1978): Interplanetary magnetic field and geomagnetic ac-
tivity. COSPAR: Space Research, Volume 18, Pergamon Press, Oxford
and New York, p. 325~328.
Gosling, J. T., J. R. Asbridge, S. J. Bame, A. J. Hundhausen, and I. B.
Strong (1967): Discontinuities in the solar wind associated with
sudden geomagnetic impulses and storm commencements. J. Geophys.
Res., 72: 3357-3363-
Hirsberg, J., A. Alksne, D. S. Colburn, S. J. Bame, and A. J. Hundhausen
(1970): Observation of a solar flare indiced interplanetary shock
and helium enriched driver gas. J . Geophys . Res. , 75:1-15-
IAGA Bulletin (I969): Geomagnetic data, rapid variations, no. 12.
Jijima, T. (1973): Interplanetary and ground magnetic conditions pre-
ceding SSC-tr igger ing substorms. Rept. Ion. Space Res. Japan,
27:205-208.
Kawasaki, K. , S.-l. Akasofu, F. Yasuharu, and C. I. Meng (1971): Storm
sudden commencements and polar magnetic substorms. J . Geophys . Res . ,
76:6761-6789.
King, J. H. (1977): Interplanetary medium data book—append ix, NSSDC/
WDC-A-R&S 77-04 A.
Kokubun, S. (1972): Relationship of the interplanetary magnetic field
structure with development of substorm and storm main phase. Plan .
Space Sci . , 20:1033-1050.
Kokubun, S., R. L. McPherron, and C. T. Russell (1977): Triggering of
substorms by solar wind discontinuities. J . Geophys . Res . , 82:
74-85.
A - 89
Moldovanu, A. (197*0: Geomagnetic effects of interplanetary sector struc-
ture. Planet. Space Sci . , 22:193-208.
Nishida, A. (1975): Interplanetary field magnetic effect on the magneto-
sphere. Space Sc i . Rev. , 1 7 : 353~ 389 •
Nishida, A. (196*0: Sudden impulses in the magnetosphere observed by
Explorer 12. J. Geophys. Res., 69:22^3-2255.
Ohdoh, T. (1970): Magnetospher ic sudden impulses. J . Rad . Res. Lab. , 17:
199-213.
Rigby, B. J., and J. S. Mainstone (1975): Characteristics of sudden
worldwide changes in the geomagnetic field. J. Atmos. Terr. Phys.,
78:92-108.
Russell, C. T., and R. L. McPherron (1973): Semiannual variation of
geomagnetic activity. J . Geophys. Res. , 78:92-108.
Shieldge, J. P., and G. L. S i scoe (1970): A correlation of the occurrence
of simultaneous sudden magnetospher i c compressions and geomagnetic
bay onset with selected geophysical indices. J. Atmos. Terr.Phys.,
32:1819-1830.
Shin, Yi-su, and A. Konradi (1975): Magnetic field depression at the
Earth surface calculated from the relationship between the size
of the magnetosphere and Dst values. J . Geophys. Res . , 80 : 1 95~ 1 99 •
A - 90
WORKING GROUP REPORT ON GEOMAGNETIC STORMS
Dr. S.-I. Akasofu
Geophysical Institute, University of Alaska
Fairbanks, Alaska 99701
1. Task definition
The task of WGB2 is to provide the scheme for the best prediction
procedures of the occurrence, intensity and time development of a geomag-
netic storm for a given flare and a given coronol hole by using the pre-
sently available knowledge. The group is charged to provide a set of
recommendations for improving the prediction procedures. For practical
purposes, a geomagnetic disturbance is defined as a geomagnetic storm when
the local K index exceeds K = 5 and/or when the Dst value exceeds 100y.
Solar flare associated storms
2.1 Prediction of the onset time
According to an extensive statistical study, the transit time of the
blast wave, namely the time interval between flare onset and storm onset
(defined by onset time of the storm sudden commencement, SSC) , is about
43 hrs; (see Fig. 1). However, when solar flares are successively generated,
the blast wave generated by the second and later flares propagate much
faster than the first wave. Thus, the transit time can become as short as
25 hrs. There does not seem to be any significant dependence of the transit
times on the central meridian distance of the responsible flares, suggesting
that the blast wave is, as a first approximation, a spherical wave.
2.2 Expected maximum intensity of the main phase decrease
Fig. 2 gives the dependence of the Dst decrease as a function of the
central meridian distance of the responsible solar flares. The envelope of
the plot can provide the expected maximum intensity of the Dst decrease.
Solar flares associated with PCA are marked by a circle with a dot. Note
that Dst decreases of more than 100y are caused by flares which are located
roughly between 45° E and 70° W. It can also be seen that PCA flares tend
to produce more intense Dst decreases than those without PCA.
2.3 Time-development of geomagnetic storms
The arrival of the blast wave to the magnetosphere (thus, the occurrence
of SSC) does not necessarily mean that a (typical) geomagnetic storm de-
velops. There is a great variety of the development of geomagnetic storms.
Some storms are associated with a large SSC (see the top example in Fig. 3),
but with no main phase. Some other storms develop a large Dst decrease
A - 91
Fig. 1
40
Ts, HOUR
Akasofu, S.-I. and S. Yoshida, Planet. Space Sci., 15, 39, 1967
0 0-
Fig. 2
-©>.
0 * * * • • ••
°.ii • © *•• •*» :. * *.
•* / /. •••■• :••.•
:• •••V -::
© e «\ V • • 8
too h . ** •*• .o
0 © 0 • <
0 ©
200
400
90*
w
» m «0» Qmw ■'■■■ ■ l — ■■
•e. *..-... »v ©. 7
• *
<
©, ?e\ . . • *. I
©,© .• ■ *• .
30* 0 30«
FLARE CENTRAL MERIDIAN DISTANCE
90*
E
Akasofu, S.-I. and S. Yoshida, Planet. Space Sci., 15, 39, 1967
A - 92
Fig. 3.
5«n.
9 A
unn
if 19.1(1
S*ri Ju»r
20 Aup
I
1959
16 U.T
20 A
UK
1959
(1) l>-
Pj
pi
ke>-
r
h"
12
4
i
12
16
4o
24
4
8
(2)
H-
■
Ho
n<
III
lu II July 1959 I'll
8 i i | - 12 i i 1 iel 1
16 U.T. 11 July 1959
20
1
24 1 1
15th M.T
Hunol
4
ill
12
8
July
1959
12
7 .
_
D-<
Honolulu 3 Die' 1958 Ml ' '
" ,2tt+|«"t~H-»-i-H *f-rt< - ■
Tfr,T^ fasten
'" tit "
Akasofu, S.-I. and S. Chapman, Solar-Terrestrial Physics,
Oxford Univ. Press, 1972.
without any distinct SSC (See the bottom example in Fig. 3). Between these
two extreme cases, there is a variety of time developments. The period be-
tween the SSC and the main phase onset is called the initial phase during
which a low latitude H component record shows a steady positive change (like
a step-function). Some geomagnetic storms have more than 10 hrs . of the
initial phase, and some others have the initial phase of only 1 hr . or less.
An important task of our WG is to find out whether or not one can pre-
dict how a geomagnetic storm will develop for a given flare. This is be-
cause major auroral activity is concentrated during the main phase of a geo-
magnetic storm, in particular during the period when the main phase is
rapidly growing and because major auroral activity causes serious iono-
spheric disturbances, power line disturbances, etc.
A - 93
This can be seen in Fig. 4 in which both auroral activity (expressed
by the AE index) and the development of the main phase (expressed by the DST
index) for the July 8-9, 1958, storm are shown.
1000 -
8
~8
2'
Fig. 4
Akasofu, S.-I. and S. Chapman, Solar-Terrestrial Physics,
Oxford Univ. Press, 1972.
A - 9^
The importance of predicting the onset of the main phase can be seen in
Figs. 5a and 5b. They show from the top, the power line fluctuations (the
GVEA line near Fairbanks, Alaska; 138KV, 100 A; 166km length, approximately
stretched along a gm meridian), the so-called 'earth current' record meas-
uring the ground electric field induced by auroral activity) and the H com-
ponent records on September 29, 1978, 02 - 19UT, (16-24 Alaska Standard Time
(AST), Sept. 28; 0-9 AST, September 29). One can see, first of all, that
most of the power line fluctuations were caused by auroral activity.
Secondly, the main phase of this particular storm began at about 07 - 08UT
Sept. 29, and the power line fluctuations began to increase considerably at
about 07 UT.
2.4 Solar wind parameters controlling the development of the main phase
One can see from the above discussion that our task is reduced to find
a solar wind parameter which controls the development of the main phase dur-
ing which auroral activity becomes intense.
It is important, first of all, at this point to examine the most appro-
priate magnetospheric quantities which represent the intensity of geomagnetic
storms. The two important 'products' of a geomagnetic storm are the Joule
heat produced in the auroral ionosphere ring current particles. Here, we
denote the Joule heat production rate by U and the ring current injection
rate by U .
K
It has been found that the solar wind parameter e defined (see
Fig. 6) by e= VB sin -^1o (erg/sec) is reasonably well correlated with
U = U + U (erg/sec)^where:
J K
V = the solar wind speed
B = the magnitude of the interplanetary magnetic field
9 = tan"' (IBy/Bzl) for Bz>0
0 = 180° - tan (IBy/Bzl) for Bz<0
Fig. 7 shows an example of this correlation for the storm of Feb. 7-8, 1967.
Fig. 8a is a good example to show that the solar wind parameter e does in-
deed control the development of the main phase. After the SSC of Sept. 23,
1966, storm at 09 UT, the main phase did not develop until about 15 UT (see
the AE index) . A large increase of the AE index was associated with the
simultaneous increase of £ at that time. One should keep in mind that in
searching the solar wind parameter it is essential to correlate it with U =
U + U . A good prediction must be based on sound physics, and it is
physically meaningless to correlate it with U alone, since U >U .
J R J
2.5 Need of monitoring the solar wind parameter
The above study indicates strongly that one can predict the time de-
velopment of geomagnetic storms by monitoring the solar wind parameter e.
A - 95
500mV/hm -
Fig. 5a Akasofu, S.-I. and R. P. Merritt, Nature, 279, 308, 1979.
,3
600y9*
1:1
24 AST
SEPTEMBER 28. 1978
SEPTEMBER 29, 1978
A - 96
INTERPLANETARY
SPACE
Magnetosphere
DISSIPATED ENERGIES
JOULE HEAT
BY
AURORAL ELECTROJET
RING CURRENT
PARTICLE ENERGY
£'VB2SIN4|^
V B SOLAR WIND SPEED
B - IMF MAGNITUDE
Uy OC AE
r
?sm
0
?sm
^0'7RE
Fig. 6
u^oc-^-Dst
IXIO" -
IX 10" -
IXIO"
IxlO"
Oistipoted Energy U • U| ♦ Uj
IMF Energy £. ( t >
16 20
7 FEB 1967
8 FEB 1967
Fig. 7
Perreault, P. and S.-I. Akasofu, Geophys. J. Roy. Astr. Soc,
54, 547, 1978.
A - 97
,18
(xl0loergs/sec)
*♦*
^
00 06 12 18
^g. 8a SEPTEMBER 23, 1966
Y
2000
1800
1600
H1400
1200
H1000,
- 800 <
- 600
400
200
24°
Fig. 8b
Origin of Plasmas in Earth's Neighborhood, Goddard Space
Flight Center, NASA, April, 1979.
98
Although it is not shown here, a number of geomagnetic storms were examined
in terms of time variations of E. Geomagnetic storms with a large SSC, but
without a significant main phase, were associated with small values of E.
It is recommended that the ISEE/C satellite data be released for
monitoring e on real time basis. It is recommended also that the IPL sate-
llite of the OPEN program is partly dedicated in monitoring £ (See Fig. 8).
It is also proposed that the exact functional form of this energy coupling
function be determined by future effort, in proving the expression of E.
3. Numerical simulation technique
It was shown in the previous section that we have now the first approxi-
mation expression for the energy coupling function E and that it is_ possible
to predict the development of geomagnetic storms by monitoring £. The
ISEE/C satellite at the libration point will be an ideal location for the
purpose.
However, the solar wind 'signal' from the libration point to the magnet-
osphere will take only about one hour or so. Therefore, it is desirable to
find other methods to infer the development of geomagnetic storms, if
possible, well before the arrival of the blast wave. It is suggested here
that the numerical simulation technique should be developed for this purpose.
Before explaining this technique, some preparation is needed. First of
all, it has become increasingly apparent that the sun has a Jupiter-like
magnetosphere, together with an extensive equatorial current disk (see Fig.
9). However, the solar current disk is not flat. It has an azimuthal large-
scale wave structure, so that as the sun rotates with a period of 27, the
earth will be located above the current disk during certain periods and be-
low it during the rest. This seems to be a better way of explaining the so-
called 'sector structure' of the interplanetary magnetic field. Further-
more, the 'root' of the current disk is not located along the solar equator
(Hundhausen) . Fig. 10 shows the root of the current disk during the
Carrington Rotation period 1616 (the thick line which connects the brightest
region of the solar corona in the lower figure) . It shows also the distri-
bution of the magnetic polarity on the solar disk and at 1 au (together with
the solar wind speed).
When a blast wave is generated on the solar disk by a solar flare (Fig.
11), it will generate a large-scale wave in the radial direction. Fig. 12a
shows schematically the wavy current disk at about 15 UT on July 5, 1974.
The inferred meridian cross-section of the solar current disk during the
July 4-5, 1974, storm is shown in Fig. 12b. Note that the situation in
Fig. 12a is shown in the fourth cross-section from the top. When the root
of the current disk is located in the southern hemisphere, a large main
phase develops if the earth is located below the wavy current disk (because
the B component is negative and 0 in £ become large); See Fig. 13. On the
other hand, if the root of the current disk is located in the northern
hemisphere, a large main phase tends to develop if the earth is located above
the current disk for the same reasons.
99
Current sheet
Current sheet
Fig. 9
Akasofu, S.-L, Space Sci . Rev., 21, 439, 1978.
Fig. 10
JULY 5,6 JUNE 27 JUNE 21
CMP JULY 15
90 180 270
CARRINGTDN LONGITUDE
JULY 9 JULY 2 JUNE 25
CARRIN6T0N 1616
360
JUNE 18
Hundhausen, A. J., Coronal Holes and High Speed Wind Streams,
Colorado Assoc. Univ. Press, 1977.
00
a
Fig. 11
6
Uchida, Y., M. D. Altschuler and G. Newkirk, Jr., Solar Phys.,
28, 495, 1973.
THE SOLAR CURRENT SHEET
Fig- 12a Akasofu, S.-I., Planet. Space Sci., 27, 1055, 1979,
A - 101
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Interplanetary magnetic field variations during a number of geomagnetic
storms were examined, and it has been demonstrated that is 'wave' inter-
pretation is more consistent with other interpretations, such as 'tangled
magnetic fields' in the ejected cloud from the sun or the 'stretched sunspot
fields' by the solar stream. The presence of the suggested magnetic field
configuration of the sun has recently been demonstrated by tracing solar
magnetic field lines by using the Type III burst field line tracing tech-
nique (Fig. 14) .
The above study suggests that if one could successfully simulate numeri-
cally the generation of the waves on the solar current disk, it will become
possible to predict the development of a geomagnetic storm well before the
arrival of the blast wave. If so, one could estimate time variations of e(t)
well before the arrival of the blast wave and thus of the time development
of geomagnetic storms on the basis of the numerical simulation. In fact,
the monitoring of e(t) at the libration point will become the 'last check'
for the prediction.
In the next section, it will be shown that such a simulation technique
has successfully made in the equatorial plane (Dryer and Wu) .
It is recommended therefore that every possible information on inter-
planetary, solar wind condition and the geometry of the solar disk be ob-
tained as initial conditions in the numerical simulation (the interplanetary
scintillation method, Solar radio Type II, IV bursts, solar protons, type IV
burst field line tracing, etc.). Soon after the flare onset, the numerical
simulation can be initiated by generating the blast wave from the flare
location.
4. Coronal-hole associated storms
The solar wind structure associated with a high-speed solar wind stream
originating from the coronal hole has extensively been studied (Fig. 15).
However, there is no obvious relationship of the solar wind quantities, such
as T, N, V, F and P independently with the AE index. This lack of correla-
tion is illustrated in Fig. 16.
However, there is a good correlation between e and the AE index (see
Fig. 17). Therefore, coronal hole-associated storms can also be monitored
by monitoring e at the libration point. It is important to note that the
solar wind parameter E is applicable to both flare-generated storms and
coronal hole-generated storms.
Coronal hole-associated storms are relatively easier to predict be-
cause of its 27-day recurrence tendency (compared with flare-generated
storms). Therefore, by monitoring carefully previous recurrence of a high
speed solar wind stream (Fig. 18), one can infer approximately the onset
date. Actually, the cause of a coronal hole-associated storm is basically
the same as a flare-generated storm in terms of the wavy structure of the
solar current disk (Fig. 19). The numerical simulation of the high speed
solar wind streams in the equatorial plane has been conducted by Dryer and
Wu. Their results can reproduce well the observed change in the equatorial
A
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EARTH
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Fig. 14
TYPE TH RADIO BURST TRAJECTORY
0900 U.T., JUNE 22,1973
SPIN PLANE OF RAE-2
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OF IMP-6
Fitzenreiter, R. J., J. Fainberg, R. R. Weber, H. Alvarez
F. T. Haddock and W. H. Potter, Solar Phys., 52^, 477
1977.
SUN
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Burlaga, L. F., Space Sci. Rev., 17, 327, 1975.
A - 104
Fig. 16
Burlaga, L. F., J. Geophys. Res., 79, 3717, 1974; the AE
index is added.
18
(MO ergs/sec)
Fig. 17
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JUNE 1974
Akasofu, S.-I., Planet. Space Sci . , 27, 1039, 1979.
A - 105
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Fig. 19
Akasofu, S.-I., Planet. Space Sci . , 27, 1055, 1979.
A - 107
plane. Therefore, it is recommended that similar numerical simulation
efforts be made in the meridian plane.
5. Magnetospheric quantities related to substorm occurrence and
intensity
It has been suggested that there are several magnetospheric quantities
which are related to the occurrence and intensity of magnetospheric sub-
storms. Some of them are:
(a) The size of the auroral oval
The size of the oval is related to the intensity of magnetospheric sub-
storms. The size of the oval can be determined and/or inferred from the
following observations :
(i) Satellite image of auroral oval (Fig. 20)
(ii) Particle flux distribution from polar orbiting satellites
(iii) Meridian chain of magnetic observatories (Fig. 21)
(b) Tail-like distortion of the magnetic field at the geosynchronous
distance
6. Substorm monitoring
The AE index is the most important substorm index at the present time.
However, it will be a difficult task to monitor the AE index on real time
basis (though not impossible) . A great international effort is needed to
achieve this purpose, by standarizing magnetometers, installing radio sets,
transmitting data to the WDC via satellites.
It has been shown that the auroral kilometric radiations correlate well
with the AE index. Fig. 22 shows an example of this correlation.
It is thus recommended that the GTL satellite of the OPEN program
carries the necessary equipment to monitor continuously the auroral kilo-
metric radiations in the magnetotail.
Fig. 23 shows another example of this correlation. Note that there
were two 'distinct' substorms on this particular day. However, the correla-
tion is not as good as one would wish. A close examination of the AE index
by the combined H component high latitude record shows that only one of the
AE stations was contributing to the two peaks. This example suggests that
there is needed for the improvement of the AE index (Rostoker) .
7. Prediction of the lowest overhead latitude of the auroral oval
It is well known that the auroral oval expands considerably equator-
wards during geomagnetic storms. Fig. 24 shows the distribution of aurorals
during the historic storm of Feb. 11, 1958. It is important to predict the
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Voots, G. R., D. A. Gurnett and S.-I. Akasofu, J. Geophys
Res., 82, 2259, 1977.
A - 11 1
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785, 1962.
A - 1 13
location of the auroral oval, since most intense ionospheric currents are
confined in the vicinity of the auroral oval and most intense particle pre-
cipitation takes place there.
There is a simple relationship between the lowest overhead latitude
(geomagnetic) of the auroral oval in the midnight sector and the Dst index
(Fig. 25). If one could predict time variations of e(t) by the numerical
simulation, it would be possible to infer the expected Dst value. Then, by
using Fig. 25, one can infer the lowest overhead latitude.
8. Identification of the source regions of the solar wind associated
with geomagnetic storms
Although solar flares and coronal-holes are identified as the source
regions of the solar wind associated with geomagnetic storms, there are
many geomagnetic storms of which the source regions on the solar disk is not
obvious at the present time. One of the recent examples of this type of
geomagnetic storms is the storm of August 28, 1978.
65°
AURORAL ARCS
SOUTHERNMOST LATITUDE - Dst(H)
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Akasofu, S.-I. and S. Chapman, J. Atmos. Terr. Phys., 24,
785, 1962.
1 1 If
ADDENDUM
WORKSHOP REPORT ON GEOMAGNETIC DISTURBANCE PREDICTIONS
J. A. Joselyn
Space Environment Laboratory
NOAA/ERL
Boulder, Colorado 80303, U.S.A.
As expressed in the previous paper, this working group sought to provide
the best available scheme for the prediction of the occurence, intens i ty , and
time development of a geomagnetic storm for a given flare or coronal hole.
As a result of the deliberations of the working group, which was chaired by
S.I. Akasofu and included S. Matsushita, F.Cook, M. Dryer, T. Watanabe, and
J. A. Joselyn, a summary logic diagram, shown in Figure 1, was drawn. The
following remarks were presented with the diagram at the closing plenary
session of the Solar-Terrestrial Predictions Workshop.
Geomagnetic effects from solar sources are extremely variable. If there
is a resultant geomagnetic storm, it may or may not have an associated sudden
commencement. Sudden impulses in the geomagnetic field associated with shocks
propagating through the interplanetary medium may or may not be followed by
a storm main phase. The actual terrestrial result of a solar cause is
apparently regulated by details at the solar source and by the ambient and
propagation characteristics of the interplanetary medium. Considering first
the possible geomagnetic impact of a solar flare, several optical, x-ray,
radio, and particle data inputs must be evaluated. These inputs are con-
veniently organized by the CFI (Comprehensive Flare Index) defined by Dodson
and Hedeman (note their report in this Proceedings). The bigger the CFI, the
bigger the potential storm and the earlier the arrival time. Arrival times
are typically on the order of 43 hours, but the range is from 25 hours to 60
or more hours. Flare location has some statistical importance to flare in-
tensity (the largest storms are identified with flares occurring between 45°E
and 70°W solar helio longitude), but not to transit times. There is essen-
tially no data available at this time to assist in predicting storm intensity
(maximum DST) and the expected length of the disturbance. Such predictions
would be useful because major auroral activity and the attendant serious
space craft, ionospheric, and long-line disturbances are concentrated during
the main phase of a geomagnetic storm.
As a possible immediate aid to short-term storm prediction, we suggest
that the solar wind plasma be monitored on a real-time basis. The I SEE -C
satellite, now orbiting the sun-earth libration point at approximately .01 AU
in front of the earth, is ideally suited for such monitoring, even though it
was not initially intended for real-time use. Solar wind plasma parameters
such as density, velocity, and magnetic field intensity and orientation could
be obtained and analyzed from 30-60 minutes in advance of the arrival of that
A - 115
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plasma at earth. Several functional forms have been suggested as algorithms
relating solar wind parameters to geomagnetic indices. These will not be
listed here except to note that there is encouraging evidence that such
algorithms are sufficiently successful that we can expect operationally useful
advance warnings, not only that a geomagnetic storm will shortly occur, but
also how large the storm will be and when it will end.
A more fundamental prediction aid, which is now being developed, is a
3-dimens ional understanding of the ambient interplanetary medium. This
understanding is required to explain why some major flares, even though suitably
located, do not precipitate geomagnetic effects. A comprehensive model of the
interplanetary medium would require the continuous integration of all available
solar observations (optical, radio, x-ray, particles, interplanetary scintil-
lation data, etc.) so that the interplanetary topology could be known and the
interaction of this pre-existing topology with flare ejecta could be calcula-
ted.
The logical sequence for geomagnetic effects originating in coronal holes
goes along the same lines as for flares. Here, the observational inputs are
ideally a0soft x-ray image, but coronal holes can also be inferred from
He J0830 A data from Kitt Peak, 'Fleurs', Australia, east-west scans at 692
and 1^15 MHz, interplanetary scintillation indications of high speed streams,
and the traditional method of recurrence. High-speed, low density plasma is
associated with a geomagnetic disturbance three to four days following the
central meridian passage of a coronal hole. The latitudinal location of the
hole is a factor - the closer to the ecliplic, the more likely that magnetic
effects will be observed. As with flares, a real-time solar wind monitoring
platform between the earth and the sun would be beneficial for short-term
predictions. And clearly, an understanding of the three-dimensional topology
of the interplanetary medium would .allow much improved long-term (days or even
months) prediction of coronal hole disturbances.
There are undoubtedly other solar sources of geomagnetic disturbances
which are yet to be fully investigated. Some of these are solar sector
boundaries, transient coronal holes, rapidly disappearing filaments, and
events beyond the visible solar limb which are still able to propagate to
earth. Work on all of these additional sources of disturbance is in progress.
An interplanetary monitoring platform is even more important for the prediction
of these events for which optical and other data may be uncertain or absent.
The final goals of an understanding of the relationship between the solar
plasma outputs and the terrestrial magnetosphere are the successful prediction
of Auroral activity (AE) and the Ring Current (DST) as inputs for global models
of currents and particle precipitation patterns. From these, spatial and
temporal gradients in the local geomagnetic field could be calculated resul-
ting in the detailed prediction of spacecraft, ionospheric, and telluric
disturbances.
Obviously, a great deal of research and technique development is neces-
sary before this prediction scheme can become operational. However, much of
the theoretical understanding implicit in the diagram now exists in at least
a rudimentary form, and additional development may allow significant improve-
ment in the near future toward the prediction of geomagnetic disturbances.
A - 117
B. MAGNETOSPHERIC PARTICLE PREDICTIONS
PREDICTION OF HIGH-ENERGY (> 0.3 MeV) SUBSTORM-RELATED
MAGNETOSPHERIC PARTICLES
D.N. Baker, R.D. Bellan, P.R. Higbie and E.W. Hones, Jr.
University of California, Los Alamos Scientific Laboratory
Los Alamos, New Mexico 875^5
Measurements both at 6.6 R„ and in the plasma sheet (>. 18 R£)
show that high-energy substorm-accelerated particles occur prefer-
entially when the solar wind speed (V ) is high. Virtually no >
0.3 MeV protons, for example, are observed in association with sub-
storms that occur when V is < 400 km/sec. On the other hand, the
probability of observing high-energy protons is very large, both at
geostationary orbit and in the plasma sheet, when V is > 700
km/sec. These results suggest that realtime monitoring of interplan-
etary conditions could allow simple, effective prediction of high-
energy magnetospheric particle disturbances.
INTRODUCTION
Measurable intensities of high-energy (0.3-2.0 MeV) substorm-related par-
ticles appear to be produced in only a small fraction (10-20J) of all sub-
storms [Hon<?g <?t al-, 1976; Belian et al.. 1978; Baker et al.. 1978]. This
occurrence frequency is generally found both for electrons [e.g. Paulikas and
Blake , 1978] and for protons. Furthermore, particles of these energies occur
with similar frequency both at synchronous altitude (6.6 R_.) in the outer
radiation zone and in the distant plasma sheet (>. 18 R„).
Absolute intensities of the high-energy particle component are generally
rather low when compared to the fluxes of other substorm-accelerated parti-
cles. Nonetheless, the very energetic particles can be quite disruptive, when
present, due to their penetrating character. Recent work has shown rather
clearly the conditions under which such particles are produced, and in this
paper we discuss simple methods for prediction of high-energy substorm parti-
cles from a knowledge of interplanetary plasma and magnetic field conditions.
INSTRUMENTATION
The measurements to be discussed in this paper were made with Los Alamos
Scientific Laboratory instruments aboard several different earth-orbiting
spacecraft. The Charged-particle Analyzer (CPA) instruments are on board
spacecraft 1976-059A and 1977-007A which are both at the geostationary orbit.
Energetic proton measurements made by various Vela spacecraft (s 18 R„) have
been described previously by Hones et al . [1976].
The CPA instrument measures low-energy electrons (LoE) and low-energy
protons (LoP). The respective energy ranges for the LoE and LoP subsystems
are 30 <. E < 300 keV and 0.15 < E < 0.6 MeV. The CPA also measures high-
energy electrons (HiE) and high-energy protons (HiP). The HiE and HiP energy
ranges are, respectively, 0.2 <. E < 2.0 MeV and 0.4 <. E < 150 MeV. Because
the geostationary spacecraft under discussion here have no onboard magnetom-
eters, pitch angle distributions of > 30 keV electrons are calculated in a
self-consistent manner (see Hiebie and Moomev [1977] and Higbie et al . ,
[1978]). Using a spherical harmonic analysis and least-squares fitting tech-
nique, the symmetry axis of the second-order (pancake" or "cigar") pitch angle
distribution of the > 30 keV electrons defines the local magnetic field direc-
tion. The colatitude (or meridional tilt) of the local field line calculated
in this way is called Q„; the second-order electron anisotropy amplitude is
called Cp. (C~ < 0 corresponds to a pancake distribution, whereas 02^*0
corresponds to a cigar distribution.)
BASIS OF THE METHOD
Figure 1 shows an example of one kind of high-energy proton enhancement
commonly observed at the geostationary orbit. Early on October 2, 1976
several substorm "injections" of lower energy (< 300 keV) protons and elec-
trons were detected by CPA instrumentation aboard spacecraft 1976-059.
Notable among these injections was that which occurred at * 0420 UT when
spacecraft 76-059 was at * 0200 LT. As seen in Figure 1, this injection event
had associated with it protons extending in energy up to at least «r 1.0 MeV.
At the higher energies (generally > 300 keV) the injected protons appeared
in the form of rather narrow, well-defined pulses of particles. Significant
dispersion is seen since higher energy channels show flux increases before
similar increases are seen at lower energies. Note that in each energy range
there are several clear pulses, or "echoes," as the protons drift azimuthally
around the earth fBelian et al. 1978].
As seen by the parameter 9fi the local magnetic field was in a very
stretched, or taillike, configuration prior to * 0430 UT, but this relaxed
toward a somewhat more dipolar configuration after the particle injection.
The highly disturbed geomagnetic conditions observed during the early
portion of October 2 are seen in the Meanook and Great Whale River magnetogram
traces shown in Figure 2. Especially noteworthy is the very large negative
bay in the Great Whale H-component beginning at * 0420 UT. This substorm
enhancement is plausibly related to the proton injection observed at 6.6 R£.
We find both drift-echo (DE) and nondrift echo (NDE) types of proton
enhancements at geostationary orbit. In contrast to the DE type of event
shown after * 0420 UT in Figure 1 , NDE events show clear flux enhancements but
by definition there is not a very evident pulsed behavior of high-energy pro-
tons in these cases.
In Figure 3 we show several different kinds of data. The upper two panels
of the figure show daily averages, respectively, of the proton and electron
intensities measured by the CPA aboard spacecraft 76-059. Selected energy
B - 2
r 0000
0KX>
0200
LOCAL TIME
0300
0400
0800
0600
0200
0900
0400
BBS
2 OCTOBER 1976
0600
i-wbo-
0866 UT
Figure 1. Selected CPA data from spacecraft 1976-059A for a portion of
October 2, 1976 including electrons in various energy ranges (as labeled) in
the upper two panels and protons in the third and fourth panels from the top.
The bottom two panels contain information (as described in the text) obtained
from the low-energy electron anisotropies: 9„ is the inferred local magnetic
field direction and CL is the > 30 keV electron second-order anisotropy
amplitude. A major feature seen in these data is high-energy proton
drift-echo event beginning at * 0420 UT (and at a spacecraft local time of ^
0200).
MEANOOK
X-COMP.
200 rt
ZOOr
GREAT WHALE
H-COMP.
1
1
1
1
OTT" 04 08
2 OCTOBER 1976
I2UT
Figure 2. Ground-based magnetogram traces from Meanook (reaches magnetic mid-
night at 0900 UT) and Great Whale River (midnight at 0600 UT) showing substorm
activity early on October 2, 2976.
ranges (out of many available) are shown for a two month period, viz.,
November- December 1976. Also shown are the 12-hour averages of the solar wind
speed, V (third panel), the interplanetary * 1 MeV proton flux (fourth
panel), the daily number of DE plus NDE events seen at spacecraft 76-059
(fifth panel), and finally, the K daily sum (sixth panel).
As may be seen, K generally correlates with V
D SW
K generally correlates with V More importantly here,
however, it is also Suggested by Figure 3 that synchronous altitude high-
energy proton and electron flux profiles, the number of DE and NDE proton
events, and even interplanetary energetic proton bursts correlate fairly well
with V .
sw
The correlation of high-energy proton enhancements at 6.6 R£ with solar
wind speed is summarized in a statistical fashion in Figure 4. The upper
panel of the figure shows the solar wind speed occurrence distribution for a
one-year period (July 1976-June 1977). The raw numbers of DE and NDE events
seen during various solar wind speed intervals are shown in the second panel.
Finally, by normalizing the panel 2 distributions by the distribution in panel
I 4 7 O 13 16 19 22 25 28 I 4 7 K> 13 16 19 22 25 28 34
NOVEMBER 1976 DECEMBER 1976
Figure 3. A composite plot of various data sets for November and December of
1976. The upper two panels show, respectively, CPA proton and electron flux
profiles at 6.6 Rg. The third panel shows the 12-hour solar wind speed
averages (courtesy of J. R. Asbridge, S. J. Bame, W. C. Feldman, and J. T.
Gosling). The fourth panel shows the interplanetary flux of 0.97-1.85 MeV
protons (Solar-Geophysical Data). The fifth panel shows the daily number of
CPA high-energy proton events observed during the period. Finally, the bottom
panel shows the November-December K daily sum, zK As discussed in the
text, several correlations between the various data sets are evident.
B - 5
800 —
600
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JULY 1976 -JUNE 1977
(CARRINGTON ROTATIONS)
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INCREASES^
DRIFT- ECHO
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NON -DRIFT- ECHO
EVENTS
200
300
400
500
600
700
V (km/s)
SW
Figure 4. The upper panel shows that between July 1976 and June 1977 the bulk
solar wind speed occurrence distribution peaked strongly between 350 and 400
km/sec. The second panel shows that most DE and NDE events occurred when V
was > 400 km/sec. When panel 2 data are normalized by the data of panel 1, a
strong positive correlation is found between proton flux increases at 6.6 Rg
and solar wind speed as shown in panel 3.
B - 6
1, we get the relative occurrence probability of high-energy proton events at
synchronous orbit.
We see that although V is < 400 km/sec much of the time during 1976-77!
relatively speaking almost no high-energy proton enhancements occur during
these low-speed conditions. However, as V increases above 400 km/sec the
probability of observing a high-energy proton enhancement increases dramatic-
ally.
This dependence on solar wind speed is not restricted to 6.6 Rg. As seen
in Figure 5, very similar results obtain for high-energy proton events
observed in the plasma sheet by Vela instrumentation. In the third panel of
Figure 5 we have normalized the probability to 100 for the 650-700 km/sec
interval. Notice the change in scale and the very strong increase in relative
probability when V > 700 km/sec.
s w
Not only the number of substorm-related events depends on solar wind
speed, but also the absolute intensity of each event depends on the associated
V . This is demonstrated in Figure 6 which shows the observed peak proton
intensities measured by the CPA plotted versus V . We have broken the
observations into three sectors according to the spacecraft location at the
time the drift-echo events were detected. As discussed by Baker et al .
[1978], the local time variation seen in Figure 6 may be related to dispersion
effects as particles move away from injection regions and also may reflect
drift-shell effects due to strong cross-magnetospheric electric fields. None-
theless, a substantial positive correlation between peak flux and solar wind
speed is seen in each local time sector.
Finally, we also find magnetospheric high-energy proton enhancements to
have a noticeable tendency to occur when the interplanetary magnetic field
(IMF) is southward. As shown by the statistical results related to Vela
observations in Figure 7, the total IMF magnitude is not abnormally large
during these events (panel (a)). However, panel (b) shows that * 95$ of the
Vela events occurred following at least a one-hour period of predominantly
southward IMF (B < 0). Panels (c) and (d) show the occurrence frequency and
median observed 0.5 MeV fluxes, respectively, plotted versus the combination
of the observed V and B for each event (i.e., the Y-component of the
SW Z -
interplanetary electric field, IEF) . Substantial dependences on the magni-
tude of the dawn-to-dusk component of the interplanetary electric field (IEF)
are suggested.
DISCUSSION AND POSSIBLE USES
The foregoing results suggest rather strongly that realtime monitoring of
the interplanetary plasma and magnetic field could permit a quite simple and
useful prediction scheme. As a minimum, users who wished to know whether or
not substorm-related particles of hundreds of keV (or above) could be expected
need only find out the solar wind velocity. This seems to be the simplest and
most fundamental correlation: if V is low, say < 400 km/sec, then high-
energy, substorm-accelerated particles are extremely unlikely throughout the
outer magnetosphere; conversely, if V is very high, say >. 700 km/sec, then
B - 7
LU
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7
z
UJ
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O
GO
O
0*
o
^-
•
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1000 —
800
600
JO 400
200 —
1
1 1
VELA PLASMA
SHEET PROTON
(>0.5 MeV) EVENTS "
1972-1974
1 1 1 1
—
—
1
3- HOUR
SOLAR WIND
AVERAGES
1
Z
o
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80
60
40
20
NUMBER OF EVENTS
NORMALIZED
BY Vsw OCCURRENCE^
300
400
500
Vsw(km/$)
600
700
800
Figure 5. Data similar to Figure 4, but for Vela plasma sheet proton enhance-
ments. In the lower panel we have normalized the relative probability to 100
between 650 and 700 km/sec. The relative probability of a high-energy proton
event increases dramatically at high V
sw
B - 8
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CPA DRIFT -ECHO EVENTS
PEAK PROTON (Ep~ 0.4 MeV)
FLUXES
2.03 xlO3- EXP (V^/128)
2.54
— 2.98 x I03- EXP (Vsw / 198)
00 LT
1
200 400 600 800
SOLAR WIND SPEED,Vsw(km/s)
Figure 6. Peak observed CPA proton fluxes (at E «r 0.4 MeV) versus bulk solar
wind speed. A positive correlation is shown by the linear regression fits to
data from each local time sector.
the probability is very high that a substorm will produce copious quantities
of high-energy protons and electrons.
There may be deeper and more detailed correlations that can be inferred
(cf., Figure 7). These more quantitative correlations appear to require
knowledge of the IMF, as well as V . Furthermore, there may be some specific
feature, such as the fluctuation spectrum of the IMF, the IEF, etc., which
B - 9
VELA PLASMA SHEET
PROTON ( Ep> 05 MeV) EVENTS
40 "
v>
<
UJ
CD
S
3
20 -
(o)
MEDIAN
1
1
I -HOUR IMF
AVERAGES
_L
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94.7 %
OF CASES HAVE
I- HOUR IMF
AVERAGES
MEDIAN
n-n
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-16 -12 -8 -4
(Bz) ,MF (gammas)
400
~ (d)
'*-■■.
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Si
.--MEDIAN OBSERVED
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FLUX
OF PROTONS
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CO
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»-
o
i
i
' 1 i
~ DETECTION
BACKGROUND
| l
i
i
!
1
2*10"'
B2VSW (V/m)
Figure 7. The dependence of Vela plasma sheet proton event occurrence fre-
quencies: (a) on the total interplanetary mangetic field (IMF) strength; (b)
on the north-south IMF component, dOjMp; and ^c^ on the Y-component of the
interplanetary electric field (IEF) which is the negative of (BZ)IMF vsw-
Part (d) shows the median observed peak proton flux in the plasma sheet versus
B V .
z sw
actually "produces" the large acceleration events observed when Vgw is high.
Nonetheless, our results suggest that whatever the mechanism, it occurs only
when solar wind speed is high; other IP changes appear to contribute in a
secondary way to this feature.
In summary, it appears that a real time monitoring of V and the IMF
could provide both a qualitative and a quantitative prediction of the proba-
bility for the occurrence and intensity of > 0.3 MeV substorm related ener-
getic particles. These predictions would seem to have validity both in the
outer radiation zones (L * 5-8) and in the magnetotail.
B - 10
AfKMnWT.EDGMENTS
We particularly thank S. J. Bame, J. R. Asbridge, W. C. Feldman, and J. T.
Gosling for providing us with solar wind data used in this study. This work
was done under the auspices of the United States Department of Energy.
BIBLIOGRAPHY
Baker, D.N., R. D. Belian, P. R. Higbie, and E. W. Hones, Jr., High-energy
magnetospheric protons and their dependence on geomagnetic and interplan-
etary conditions, submitted to J. Geophvs. Res. . 1978.
Belian, R. D., D. N. Baker, P. R. Higbie, and E. W. Hones, Jr., High-
resolution energetic particle measurements at 6.6 RE» 2, High-energy
proton drift-echoes, J. Geophvs. Res. . §£., 1978.
Higbie, P. R. and W. R. Moomey, Pitch angle measurements from satellites using
particle telescopes with multiple view directions, Nucl. Instr. and Meth. .
JM, 439, 1977.
Higbie, P. R. , R. D. Belian, and D. N. Baker, High-resolution particle meas-
urements at 6.6 RE, 1, Electron micropulsations, J. Geophys. Res. . 83.,
1978.
Hones, E. W. , Jr., I. D. Palmer, and P. R. Higbie, Energetic protons of mag-
netospheric origin in the plasma sheet associated with substorms, J_,_
Geophvs. Res.r £l, 3866, 1976.
Paulikas, G. A., and J. B. Blake, Energetic electrons at synchronous altitude
1967-1977, Aerospace Corporation Rep. No. TR-0078 (3960-05), March 1978.
Solar Geophysical Data, Environmental Data Service, NOAA, Nos. 393 and 391*,
May- June, 1977.
B - 11
THE USE OF > 30 keV ELECTRON ANISOTROPICS AT 6.6 R.
TO PREDICT MAGNETOSPHERIC SUBSTORMS *
D. N. Baker, P. R. Higbie, E. W. Hones, Jr., and R. D. Belian
University of California, Los Alamos Scientific Laboratory
Los Alamos, New Mexico 87545
Observations at the geostationary orbit show that > 30 keV elec-
tron pitch angle distributions begin to develop a cigarlike (field-
aligned) character typically one to two hours prior to the onset of
the injection of substorm-produced energetic particles into the outer
radiation zone. Conversely, when no substorm is imminent the low-
energy electrons remain nearly isotropic in the nighttime magneto-
sphere. The direct substorm injection of particles is usually
detected near local midnight whereas the cigarlike anisotropics are
generally detected when the spacecraft is in the (pre)midnight sector
(18-02 local time). These results suggest that 30 keV electron
field-aligned anisotropics at 6.6 R„ may serve as a short-term (0.5-
3.0 hour) predictor of substorms. Real time monitoring of a simple
electron anisotropy parameter from a network of well-instrumented
spacecraft could aid in the operation of military and communications
satellites and could also help predict ionospheric disturbances.
1 . Introduction
Accurate, short-term (0.5-3.0 hour) prediction of magnetospheric substorms
and substorm-related effects would be of great potential benefit. For exam-
ple, spacecraft charging events and other operational anomalies often occur in
association with substorm injection events at the synchronous orbit of 6.6 Rp
fGarrett et al . . 1977]. Thus, a simple, reliable method of forecasting the
imminence of a substorm could allow spacecraft operation personnel time to
prepare for these difficulties and possibly take alternative or preventive
measures.
The primary disruption due to substorm-produced hot plasma and energetic
particles generally occurs in the 23-06 local time (LT) sector fGarrett et
al . . 1977]. Hence the danger to spacecraft operations, and also for iono-
spheric disturbances resulting from substorms, occurs with highest probability
as the spacecraft (or the conjugate ionospheric region) moves into the mid-
night sector. Of course, injected plasmas and energetic particles may readily
drift in azimuth around the earth, but the first impulsive appearance of the
disturbance is near midnight f Parks et al. . 1968; Arnoldv and Chan. 1969;
Baker et al. , 1978].
*Work performed under the auspices of the U.S. Department of Energy, Washington
DC B - 12
As will be discussed in this paper, we find that in situ measurements of
the anisotropy of > 30 keV electrons at synchronous orbit appears to provide a
tool for assessing the probability of an impending substorm. The method may
be viewed as either a very limited technique or as a general predictive scheme.
In the limited sense, the anisotropy measurements could simply aid in the
operations of a given spacecraft bearing electron detectors similar to those
to be discussed below. As part of a more expanded technique, however, more
general information for substorm prediction may be obtained from energetic
electron anisotropics and therefore the method could be of general predictive
utility.
2. Instrumentation
The observations to be discussed in this paper were obtained with the
low-energy electron (LoE) detector portion of the Los Alamos Scientific
Laboratory Charged-Particle Analyzer (CPA) experiments. Identical CPA instru-
ments are onboard spacecraft 1976-059A and spacecraft 1977-007A both of which
are located in geostationary orbit. For the period under discussion here,
77-007 was at <^ 135° W longitude, while 76-059 was first at <^ 35° W and then
was at * 70° W longitude.
The LoE sensors measure energetic electrons in the energy range 30 to 300
keV with six fixed energy discrimination thresholds. Each LoE detector con-
sists of five identical sensor-collimator units arranged at 0° , ±30° , and +60°
to the spacecraft equatorial plane. The spacecraft rotates with a ten-second
period around an axis that points continually toward the center of the earth.
Given the fan detector arrangement and given the high sampling rate of the
instrument, we obtain a set of 200 data points at each energy level during
each ten-second rotation. Furthermore, these points are spread rather uni-
formly over the unit sphere and this allows complete, continuous pitch angle
coverage for all magnetic field orientations.
Since the spacecraft under consideration here have no onboard magnetome-
ters, pitch angle distributions are computed in a self-consistent manner from
the > 30 keV electrons using a spherical harmonic analysis and least-squares
fitting technique fHigbie and Moomev. 1977]. Quite accurate field directions
can be inferred by this technique, but no information about field magnitudes
is obtained.
The spherical harmonic analysis includes terms up to, and including, the
fourth order. Of particular relevance here is the character of the second-
order anisotropy. The amplitude of the second-order anisotropy is called C2:
if C is > 0, this corresponds to a field-aligned type of anisotropy which we
generally designate as a "cigar" distribution; if C? is < 0, this corresponds
to a trapped type of distribution (j at a = 90°) which we call a "pancake"
distribution. The symmetry axis of the second-order, trapped distribution
(cigar or pancake) defines the local magnetic field direction. The colatitude
(or meridional tilt) of the field line calculated in this way is designated as
6g. In a dipolar magnetic field, 9g would be expected to be twice the mag-
netic latitude of the geostationary spacecraft (i.e., 10°-20°). As will be
seen below, significant "stretching" of the field lines (0 > 20°) often
occurs in the nightside magnetosphere .
B - 13
LOCAL TIME
06 07
SEPTEMBER 8,1977
08 UT
Fig. 1. Charged-particle analyzer low-energy electron data for a portion of
September 8, 1977 as measured by spacecraft 1977-007A at geosta-
tionary orbit. The upper panel shows differential electron fluxes in
the energy ranges (keV) as labeled. The second panel shows the
inferred meridional tilt (9fi) of the local magnetic field line, while
the third panel shows the > 30 keV electron second-order anisotropy
parameter (C?) .
3. Basis of the Method
Figure 1 shows data obtained from the CPA aboard spacecraft 1977-077 for <
portion of September 8, 1977- The top panel shows differential electron
intensities between 30 and 300 keV as labeled. The second panel shows the
inferred tilt, 8 , of the local magnetic field line. The bottom panel shows
the second-order anisotropy parameter, C_. Universal time (UT) of the data
acquisition is shown along the bottom of the figure, while spacecraft geo-
graphic local time (LT) is shown along the top of the figure.
Electron fluxes as observed by spacecraft 77-007 had been approximately
constant since 0300 UT (1800 LT) . Beginning at ^ 0530 UT (2030 LT) the Cp
parameter increases substantially indicating the progressive development of a
cigarlike electron anisotropy. Concurrent with the increase of C , the spin-
averaged electron flux at all energy levels diminishes gradually and nearly
monotonically.
B
14
At <r 0620 UT, C? increases more rapidly and reaches +1.0 by 0700 UT.
During this same time interval 0R increases substantially to * 50°. Prior to
0500 UT 9R was * 15° which would be only a slightly larger field line tilt
than expected in a dipolar field (i.e., 9 ^ 10° at the spacecraft magnetic
latitude of <r 5°). Hence, throughout the "cigar phase" of this event there
was a progressive development of a more stretched or "taillike" field in the
premidnight sector of the magnetosphere.
At ^ 0720 UT we observe an injection of energetic electrons in essentially
all energy ranges up to 300 keV. At nearly the same time C_ decreases
abruptly and goes negative indicating that the > 30 keV electron anisotropy
has become of the pancake, or trapped, variety with peak fluxes perpendicular
to the local field line. Concurrent with these flux and anisotropy changes,
it is seen that 9 relaxes from <r 50° back to 15° * 20°. Hence a more dipolar
configuration of the field accompanies the injection process.
In Figure 2 we show the detailed character of the pitch angle distribu-
tions of the electrons at several points during the event shown in Figure 1 .
Each vertical column of Figure 2 shows pitch angle distributions at selected
energy levels (as labeled to the right of the figure) and each column corre-
sponds to data acquired during one 10-second spacecraft rotation beginning at
the time indicated at the top of the figure. Each individual distribution
corresponds to the number of counts per 8-msec sample plotted versus p = cosa .
As shown by the 0604:43 UT samples, the > 30 keV anisotropics early in the
precursory phase begin by showing a mild, but clear, flux minimum at u = 0 (a
= 90°). Later at 0701:23 UT when the field is rather taillike (eB ^ 50°) and
C_ is large (+1.0), the flux minimum at m = 0 is very pronounced. We find the
cigar anisotropics prior to substorms to be readily detectable with the CPA
even for 0B values approaching 80° -90° f Baker et al. . 1978].
After the substorm onset and the concomitant flux injection, we see strong
flux maxima at u = 0. As illustrated by the third column of Figure 2 (0802:49
UT), this pancake character extends, in this case, only up to £ 100 keV
whereas at higher energies the electrons merely resume an approximately
isotropic distribution.
The relationship that these energetic electron variations bear to sub-
storms is shown by Figure 3. Leirvogur (* 22° W geographic longitude) shows
two periods of substorm activity beginning at * 2200 UT of September 7 and *
0120 UT of September 8. At Meanook (* 113° W geographic longitude) slight
disturbances are seen after <r 2200 and <r 0100 UT. There is only one clear
substorm signature at Meanook, however, and the onset time for this event is *
0720 UT. Thus the energetic electron injection seen at spacecraft 77-007 {?
135° W longitude) corresponds almost precisely to the small, 100 y bay onset
seen at Meanook. Furthermore, the cigar anisotropy phase (0530-0720 UT)
occurs well after substorm activity has ceased at magnetometer stations near
midnight at that time.
Most energetic electron injections which we observe near midnight at 6.6
R£ follow a pattern similar to that illustrated in Figure 1. That is, there
is a "precursory" phase in which significant taillike stretching of the field
lines occurs and a substantial cigar type of anisotropy is observed in the >
B - 15
16
20 00
n i r
500y
04
08 UT
500
MEAN00K
H
500 y
J L
1
20
00 04 08
SEPTEMBER 7-8 1977
12
Fig. 2. Pitch angle distributions observed at selected times during the event
shown in Figure 1. Several electron energies, as labeled on the
right, are shown and each plot corresponds to the number of counts
per 8 msec sample versus u, the cosine of the pitch angle (a).
30 keV electrons. At the time of the flux injection (which is usually very
close to the substorm expansion onset as determined from ground-based mag-
netometer data) the 30 keV electrons exhibit a strong pancake distribution.
We have examined several month's worth of data to assess the statistical
association of the cigar phase (in > 30 keV electrons) at 6.6 RE with sub-
storms. Table 1 is a matrix representation which summarizes our results from
available data during July-December 1976. Included are substorms which
occurred when the spacecraft was within several hours of local midnight.
Several points should be noted in Table 1. First, we had no AE indices
available for this study and thus we had to rely on standard auroral zone
magnetograms (Kiruna, Leirvogur, Narssarssuaq, Great Whale River) to judge
whether or not a substorm had occurred. Secondly, the 17 cases in which no
cigar phase was observed correspond to passages of the spacecraft completely
through the nighttime sector of the magnetosphere. Hence the numbers in row 1
B - 16
0604:43 UT
070I.23UT
0B--48°
0802:49 UT
0B=I6*
50
25
0
30
I5|
0
20
IOJ
0
10
5. ...
0
0
JJ = COSCX
600
300-
0
I00{
50
0
30
15
0
15'
10-
54
0
0
+ 1
>
UJ
o
>
UJ
m
CD
>
>
ui
o
Fig. 3. Ground-based raagnetogram traces for 7-8 September, 1 977 showing
auroral zone substorm activity associated with the period shown in
Figure 1 .
of the table are a different entity than the event-related numbers of row 2.
Nonetheless, the rather highly diagonal character of the matrix in Table 1
suggests a firm relationship between the cigar phase and substorms.
To further assess the statistical relationship of the cigar phase to sub-
storm onset we have generated distributions such as that shown in Figure 4.
For approximately 85 events in which we observed flux injections at the
B - 17
TABLE 1
PRECURSORY CIGAR-PHASE ASSOCIATION WITH SUBSTQRMS,
No
Sub storm
Substorm
Observed
No
Cigar-Phase
Observed
Cigar-Phase
Observed
15
97
T
MEDIAN
20
UJ
</)
<
o
en
UJ
CD
10
i
CIGAR ONSET TIME
RELATIVE TO
FLUX INJECTION TIME
1
100
200
(min)
300
Fig. 4. The statistical relationship of the onset of the cigar phase in the >
30 keV electrons at 6.6 R„ to the observed flux injection time on the
same spacecraft. The value of t is the flux injection time minus the
cigar phase onset time.
B - 18
synchronous orbit satellite in the midnight sector and in which we could
assign a clear cigar-phase onset time, we have found the time, t, between the
onset of the cigar phase and the injection time. At least as far as the
spacecraft at 6.6 R„ is concerned, "flux injection time" is synonymous
with "substorm onset time." As shown by Figure 4, > 85% of the substorm
injection events had cigar phases < 3 hours in duration. (The significance or
importance of the extended tail of the distribution in Figure 4 remains to be
assessed.) The typical (median) time of duration of the cigar precursory
phase was found to be * 1.5 hours.
We conclude from these results that the observation of cigarlike anisot-
ropics in > 30 keV electrons at 6.6 R„ implies with high probability that a
substorm will occur shortly. Similarly we conclude that absence of cigar
anisotropies implies, again with high probability, that no substorm is
imminent. Observation of the onset of the cigar phase (which occurs primarily
only in the 18-02 LT sector) can mean that the disruption associated with
energetic particle and hot plasma injection can occur any time between ^0.5
and ^3.0 hours later. However, the highest probability is that the next
injection of particles will occur in about one to two hours.
4. Discussion and Possible Uses
As described in the Introduction, one of the major impacts of substorms is
the disruption of spacecraft operations due to energetic particle (and hot
plasma) disturbances generated during the substorm. Many other impacts (such
as ionospheric disturbances, communications interruption, etc.) of a very
practical nature also occur as a result of these energetic particle substorm
effects. Thus it seems reasonable that all methods of predicting such events
(and thus alleviating their impact) should be employed.
We feel that we have a reasonably good theoretical understanding of why a
"cigar phase" should accompany most substorm events. The reason is that in
the nightside magnetosphere the synchronous altitude is right on the border-
line at which * 30 keV electrons are ordinarily nearly isotropic (or else have
a pancake distribution) in the undistorted, quiescent magnetosphere. As the
magnetosphere becomes more distorted with the development of a stretched,
taillike magnetic field geometry on the nightside, the * 30 keV electrons
respond very sensitively. In the stretched field topology, small pitch angle
electrons drift further from the earth than they normally would in the
quiescent magnetosphere, while large pitch angle electrons drift nearer to the
earth than normal. Both of these populations drift in this way in an attempt
to preserve their adiabatic invariants fRoedererf 1972]. Since there are weak
(but noticeable) radial gradients in the 30 keV electron population in the
outer radiation zone, the net result of the distorted drift paths discussed
above is to produce cigarlike anisotropies at L - 6.6. This ordinarily occurs
if, and only if, substantial stresses have built up in the outer magneto-
sphere, i.e., if, and only if, a substorm is imminent. Eventually the accumu-
lated magnetic stress in the magnetotail is released by the substorm and the
field at 6.6 R„ relaxes toward a more dipolar configuration.
Ei
Our observations are generally consistent with the well-known model
[ McPherron et al. , 1973] of substorms in which a southward IMF causes dayside
raagnetopause erosion, flux transport to the tail lobes (with an increase in
B - 19
tail lobe field strength), and an increase and inward motion of the cross tail
current. This latter inward motion of the tail current then produces a more
taillike field geometry in the vicinity of 6.6 PL and energetic electrons
respond as described above.
Energetic electrons, we feel, offer certain advantages over synchronous
orbit magnetometers in observing substorm-induced magnetospheric effects:
(1) Electrons, in a sense, average over a broad range of magnetospheric longi-
tudes by virtue of their eastward azimuthal gradient and curvature drifts,
whereas individual magnetometers make very localized measurements; and
(2) Electron anisotropics can often show enhanced cigarlike character even
when concomitant significant taillike field stretching is not observed at a
given spacecraft location. The latter effect may well reflect the fact that
electron cigarlike anisotropics may often result (or be enhanced) by the
losses of a ^ 90° particles at the dayside due to the dayside magnetopause
erosion mentioned in the model above. Magnetometers cannot show such evidence
of dayside erosion directly. We point out that the electron measurements dis-
cussed here can be made by suitably instrumented spacecraft on which energetic
particle background levels are routinely and importantly measured. This can
be done without the additional requirements of high magnetometer telemetry
rates and extreme spacecraft cleanliness. We certainly would not, however,
wish to argue that magnetometer data are not desirable and important for most
scientific endeavors at any magnetospheric location.
Although we are advocating use of electron anisotropics to predict sub-
storms, we are not arguing for causality. Certainly, cigarlike energetic
electron anisotropies do not "cause" substorms, nor does a certain degree of
taillike magnetic field stretching necessarily imply that a substorm will
occur in some specific period of time. Our observations do, however, suggest
that once magnetospheric stresses have been built up they will, in general,
only be relieved by a substorm occurrence. Thus our results show a statisti-
cal relationship between the time of cigar phase onset and the time of sub-
storm expansion phase onset with a typical difference in these times of 1-2
hours. Embedded within this statistical relationship may well be a direct
physical causality associated with time scales of instability onsets or times
for certain sequences of processes to lead to the eventual energy release of a
substorm. Further research will hopefully answer this question.
The results reported here appear to support the concept of a substorm
"growth phase" [Mc^herron, 1970], at least for substorms which we are able to
observe at synchronous orbit. There is apparent disagreement at this time as
to whether every individual substorm has a growth phase as described by
McPherron, or whether there is only a single growth phase (following a south-
ward turning of the IMF) which precedes a sequence of substorms (see Pvtte and
West [1978] for a recent discussion of the growth phase). Our results seem to
indicate that nearly every observed substorm is preceded by the 'cigar phase1.
Whether this phenomenon indicates a growth phase for individual substorms, or
simply the reestablishment of conditions (say by electrons newly drifting to
the spacecraft location) due to an earlier addition of energy to the magneto-
tail, is a subject for further research. We again note that the cigar phase
may be quite evident in the 30 keV electrons even though there is little
apparent progressive taillike magnetic field stretching at 6.6 Rg and even
B - 20
though ground-based magnetometers may show little departure from quiet-time
behavior.
Observations relating specifically to the growth phase of substorms have
been presented, for example, in the series of papers about the August 15,
1968 substorms (see McPherron [1973] and the papers thereafter). Detailed
electron anisotropy information is given for these cases by West et al.
[1973b] and Kivelson et al. [1973]. 0G0 5 observations of two substorms, made
near midnight at a greater geocentric distance than our own observations,
showed a transition of the electron pitch angle distributions (E > 50 keV)
from field-aligned to approximately isotropic during the substorm growth phase
identified by a variety of other observations. Thus, our results at 6.6 RE
for a very large number of cases would indicate an association of the growth
of the cigar distributions of electrons (E > 30 keV) with a substorm "growth
phase," whereas the previous observations at generally greater geocentric dis-
tances have associated the disappearance of cigar anisotropics with the growth
phase. It is felt that all of these observations are generally consistent
with the expected behavior of drifting electrons in a distorted magnetospheric
field.
As in Figure 1 above, we have studied many examples of fairly "isolated"
substorms. We observe quite frequently, however, many substorms in rapid
succession each with accompanying energetic particle injection. Ordinarily
the period prior to each of these several injections is accompanied by the
return or re-establishment of the cigar phase. This continues, apparently,
until all of the available free energy has been dissipated and the magneto-
spheric ground state is approached. Thus, even under very disturbed condi-
tions the cigar phase or the time derivative of the C parameter may be used
to indicate that yet another substorm onset and flux injection is imminent.
Recently it has been proposed [Akasofu, 1978] that realtime monitoring of
the solar wind velocity (V) and the interplanetary magnetic field (IMF) magni-
tude and direction could predict substorms (or at least the AE index) with
50-60 % probability. This seems, indeed, to be a very promising approach.
This corresponds to an external monitor of the energy input function. From
our present results, we would suggest that low-energy electron anisotropies
appear to act as a rather sensitive internal magnetospheric "barometer." To
achieve the highest success in substorm prediction, it would seem profitable
to use several effective means of prediction including both external and
internal assessment methods.
A set of several well-instrumented synchronous altitude satellites sepa-
rated from each other by several hours in local time could form a very useful
substorm monitoring network. Real time readout and assessment of a very
simple electron parameter (such as C~) in the local nighttime sector could
give a reasonably good handle on the probability of an imminent substorm.
This information could be used not only in the operation of military and com-
munications satellites, but also to predict ionospheric disturbances associ-
ated with the drifting injected energetic particles.
B - 21
Bibliography
Akasofu, S.-I., Interplanetary energy flux assoociated with magnetospheric
substorms, Univ. of Alaska Geophys. Inst, preprint, 1978.
Arnoldy, R. L. , and K. W. Chan, Particle substorms observed at geostationary
orbit, J. Geophvs. Res. . 74. 5019, 1969-
Baker, D. N. , P. R., Higbie, E. W. Hones, Jr., and R. D. Belian,
High-resolution energetic particle measurements at 6.6 RE» 3, Low-energy
electron anisotropies and short-term substorm predictions, J. Geophvs.
Res. . 81, 4863, 1978.
Garrett, H. B. , A. L. Pavel, and D. A. Hardy, Rapid variations in spacecraft
potential, Air Force Geophys. Lab., Rep. AFGL-TR-77-0132, 1977-
Higbie, P. R. , and W. R. Moomey, Pitch angle measurements from satellites
using particle telescopes with multiple view directions, Nuc. Inst, and
Meth. . _14_. 439, 1977-
Kivelson, M. G. , T. A. Farley, and M. P. Aubry, Satellite studies of magneto-
spheric substorms on august 15, 1968, 5, Energetic electrons, spatial
boundaries, and wave particle interactions at Ogo 5, J. Geophvs. Res. . 78.
3079, 1973.
McPherron, R. L. , Growth phase of magnetospheric substorms, J. Geophvs. Res. .
23., 5592, 1970.
McPherron, R. L. , Satellite studies of magnetospheric substorms on August 15,
1968, 1, State of the magnetosphere , J. Geophvs. Res. .78. 3044, 1973-
McPherron, R. L. , C. T. Russell, and M. P. Aubry, Satellite studies of mag-
netospheric substorms on August 15, 1968, 9, Phenomenological model for
substorms, J. Geophvs. Res. . 78. 3131, 1973.
Parks, G. K. , R. L. Arnoldy, T. W. Lezniak, and J. R. Winckler, Correlated
effects of energetic electrons at the 6.6 Rp equator and the auroral zone
during magnetospheric substorms, Rad. Sci . . 3., 715, 1968.
Pytte, T., and H. I. West, Jr., Ground-satellite correlations during
presubstorm magnetic field configuration changes and plasma sheet thinning
in the near-earth magnetotail , J. Geophvs. Res. . 8^. 3791, 1978.
Roederer, J. G. , Geomagnetic field distortions and their effects on radiation
belt particles, Rev. Geophvs. Space Phvs.. 10. 599, 1972.
West, H. I., Jr., R. M. Buck, and J. R. Walton, Satellite studies of
magnetospheric substorms on August 15, 1968, 6, Ogo 5 energetic electron
observations - Pitch angle distributions in the nighttime magnetosphere,
J. Geophvs. Res.. 78. 3093, 1973-
B - 22
EVOLUTION OF SUBSTORM AND QUIET-TIME ELECTRON ANISOTROPIES
(30 i E i 300 keV) AT 6.6 Rp
P. R. Higbie, D. N. Baker, R. D. Belian, and E. W. Hones, Jr.
University of California, Los Alamos Scientific Laboratory
Los Alamos, New Mexico 87545
Work using the Charged Particle Analyzer (CPA) instruments
aboard spacecraft 1976-059A and 1977-007A in synchronous orbit has
shown that * 30 keV electron anisotropics may act as a sensitive
indicator of the buildup of stresses in the outer magnetosphere. The
development of such stresses is evidenced in the premidnight sector
by the formation of field-aligned (cigar) anisotropics in the 30 keV
electrons one to two hours prior to the onset of the expansion phase
of the substorm. Using the complete three-dimensional pitch angle
measurement capability of the CPA, we show in a movie format the
detailed development of electron anisotropics during the course of
substorm growth, expansion, and recovery phases. In contrast, we
also show detailed examples of quiet-time behavior of electron
anisotropics at several energy levels between 30 and 300 keV. Such
periods with no substorm activity show that 30 keV electrons remain ^
isotropic (outside the loss cone) throughout the nighttime sector,
even though the higher energy (> 100 keV) electrons show the develop-
ment of cigar anisotropics associated with normal drift-shell split-
ting. These results emphasize the substorm predictive capabilities
of the low-energy electron anisotropics and illustrate how the data
might be used in a real-time monitoring mode.
INTRODUCTION
Numerous authors have studied the correlations between the interplanetary
magnetic field (IMF) and ground based observations of geomagnetic activity.
Caan et al. [1977] examined 18 clear events for which the IMF turned southward
after being directed northward for at least two hours. Such turnings were
followed in about one hour by substorms as determined from magnetograms
recorded at nightside auroral or midlatitude stations. The beginning of some
negative bays were correlated with momentary northward excursions of the IMF
and the recovery phases of the substorms, as indicated by the magnetograms,
seemed to be controlled by the northward turning of the IMF.
Kamide et al. [1977] examined electron precipitation data from Isis 1 and
2 as well as all-sky camera data to determine if the substorm occurrence
probability was related to the B component of the IMF or to the size of the
auroral. They found that the "storm time" probability increased from a low
but appreciable value for distinctly northward fields to 10051 for strongly
southward fields. Conversely, the "quiet time" probability decreased to zero
for even weakly southward fields.
B - 23
Burton et al. [1975] developed an empirical equation relating Dst to
interplanetary conditions. They found that Dst, which is mainly responsive to
the ring current and is calculated from an average of the perturbations of the
H component at mid-latitude stations, could be approximated by a function of
the solar wind dynamic pressure and the Y component of the interplanetary
field (rectified to correspond to B southward) in solar magnetospheric coor-
dinates. They also introduced a filter function to account for" delays in the
response of the magnetosphere to changing solar wind conditions. This served
the same purpose as the typical one hour time lags used by other authors
investigating such correlations.
In an earlier paper by Hirshberg and Colburn C 1969] > the magnitude of the
three-hour averaged B component was found to be correlated with K regardless
of the sign of B . On the other hand, the variance in B was found to be posi-
tively correlated with K when B was negative.
The preconditions for triggering of a substorm by solar wind discontinui-
ties were examined by Kokubun et al. [1977]. They compared ground magneto-
grams and AE indices with interplanetary field data for 125 storm sudden com-
mencement (SSC) and sudden impulse (Si) events. They found that the probabil-
ity of a substorm being triggered increased with the amplitude of the SSC and
was strongly dependent on the previous AE activity and the (southward) direc-
tion of the IMF. They also cited a few cases in which the energy required for
a substorm occurrence was not stored effectively although the IMF was south-
ward.
McPherron [1970] established the concept of a growth phase for a geomag-
netic substorm. While the signature in the magnet ograms for a given substorm
may be subjective, the idea that the build-up, prior to a substorm, of mag-
netic stresses or the inflow of magnetic energy to the magnet otail might have
observable consequences is quite reasonable.
Kamide and Matsushita [1978] presented a summary of the growth phase con-
troversy and attempted to reconcile the differences in a consistent manner.
They view the source (dayside merging), energy storage (excess flux in the
magnetotail) , and drain (reconnected nightside flux) as separate processes.
The drain process may proceed quietly (as by plasma convection) or catastro-
phically (as in sub storms) . The source, storage and drain processes are
related, but not in a simple deterministic way. In Kamide and Matsushita's
view, the growth phase narrowly defined applies to very few substorm occur-
rences, and broadly defined applies to almost all configurations of the
magnetosphere .
Perreault and Kamide [1976] cited a number of cases for which the IMF was
not uniform across the face of the magnetosphere. Several cases were found
when the field was oppositely directed upstream of the dawn and dusk sectors
respectively. This result implies care should be taken in relating magneto-
spheric effects to possible external driving forces.
Svalgaard [1977] gave a very detailed treatment of the am index and was
able to synthesize a function using solar wind parameters (plasma density,
bulk speed, the angle between the IMF and the dipole axis, the dipole tilt
B - 2k
angle, and the magnitude and variance of the IMF) which replicated the index
almost exactly.
The phenomenon of drift-shell splitting is well known and analyzed
(Pfitzer et al. [1969], Roederer [1972]). The fact that particles of the same
energy but having different initial pitch angles have orbits lying on differ-
ent drift shells in a nonazimuthally symmetric magnetic field will play a key
-role in the analysis given below. In our remarks below we will suggest that
-stored magnetic energy or stresses in the magnetotail indeed has observable
consequences for energetic electron distributions.
A number of groups have observed particles at geostationary altitudes and
have studied their relation to substorms as well as their typical behavior.
Parks et al. (1972) summarized a number of features of energetic particle
variations observed at the geostationary orbit and suggested a model of mag-
netospheric substorms. They found that the intensity of fluxes of electrons
in the 5QQ-keV to 1 MeV energy range are well organized by the quantity
(0.31 1/B) where B is the locally measured magnetic field. Temporal varia-
tions are more apparent in the 50-150 keV energy range. The intensity of
precipitated fluxes (inferred from x-ray observations from balloons) are
intimately related to the intensity of these particles at the equator. After
being accelerated in the morning hours, these electrons gradient drift east-
ward, but are nearly all precipitated before reaching the evening hours in
local time.
Parks et al. further suggest that the recovery of the magnetic field to a
more dipolar orientation is a consequence of the removal of a high g plasma
from the lines of force as the electrons (E «r 10 keV) are precipitated.
Precipitation is due to the growth of whistlers (Kennel-Petschek mechanism) .
The recovery of the field accelerates the electrons by betatron action and
enhances the pitch-angle anisotropy. As the local electron fluxes are
depleted the field becomes more dipolar and field lines further out in the
tail begin to dump their associated hot electrons. This corresponds to the
poleward auroral expansion phase. This model thus suggests that substorms are
initiated by strong precipitation of energetic electrons on the morning side
of the magnetosphere . This process depends on the state of the magneto sphere
and the constantly changing solar wind parameters and ionospheric parameters.
Pitch angle distributions at geostationary altitudes have been studied by
several authors (Bogott and Mozer, 1971; Kaye et al . . 1978; Higbie et al. .
1978b). In general they find evidence for drift shell splitting effects. In
addition Kaye et al. find evidence for strict local control of the pitch angle
distributions in that the distributions respond adiabatically to changes in
the local magnetic field.
Baker et al. (1978a) observed that the existence of cigar anj^otropies in
the late evening to midnight range at the geostationary orbit couid be taken
as a prediction of substorm onsets. In some 97 cases cigar anisotropics were
seen to preceed substorms, whereas for 17 cases when no cigars were seen, only
two were accompanied by (weak) substorm activity. This paper illustrates in a
movie format the evolution of typical observations of this type.
B - 25
INSTRUMENTS AND MOVIE FORMAT
The charged particle analyzer has been described in some detail previously
(Higbie. et al. 1978b). Briefly, five collimated sensors are arranged at 30 ,
60 , 90 , 120 and 150 to the spacecraft spin axis which is always pointed
toward the earth. Each sensor is sampled, for each of six energy windows,
forty times per ten second rotation period. Thus for each energy there are
two hundred samples which cover the unit sphere rather uniformly. The energy
windows have 30, 45, 65, 95, 140, and 200 keV thresholds with a common upper
energy cutoff of 300 keV. Since there is no on-board magnetometer the pitch
angle distributions must be calculated in a self consistent manner (Higbie and
Moomey, 1977).
In the movie the pitch angle distributions are plotted as a function of
the cosine of the pitch angle (measured from the symmetry axis of the distri-
bution) and are illustrated at the top of each frame. The six energy windows
corresponding to each distribution increase from left to right and top to
bottom. The normalized counting rate (or square root for compression) is
plotted in each box.
The spin-averaged counting rate corresponding to the lowest energy window
is plotted in the lowest panel. Since each movie frame corresponds to one
spacecraft rotation, the movie proceeds at approximately 1 80 to 240 times real
time for silent or sound projection rates. One point is added to the spin-
averaged counting rate curve for each movie frame so that the end point of the
curve serves as a time reference.
Also plotted for certain examples are the B component of the IMF in solar
magnetospheric coordinates and the auroral zone magnetometer readings for a
ground station near the spacecraft meridian.
OBSERVATIONS
October n, 1976 Event
Prior to the start of the movie the IMF had gone through a two and one-
half hour period (2100-2300) of strong negative B , an hour and a half episode
of positive>B and then another half-hour of negative B . At the start of the
movie B has just turned northward. The C? parameter is very large and posi-
tive indicating strong cigar development. All energy channels show well
developed cigar shapes, as illustrated in Figure 1a. Close inspection of
these distributions reveals a small loss cone very near y - + 1. The distri-
butions evolve slowly during the next two hours. The spin averaged counting
rate does not change appreciably, but by 0400 UT there has been an appreciable
relative increase of 90 pitch angle particles at all energies (Figure 1b).
At 0409 UT there is a slight decrease in thr spin average counting rate which
occurs s 2 minutes after the IMF has turned southward momentarily. During the
next hour the velocity of the solar wind increases from «/> 450 to ^ 480 km/sec
and its density decreases by a factor of three. 90 pitch angle particles
begin to appear at 18310 sec UT, apparently at all energies simultaneously.
These particles are particularly evident in channels 3 and 4 in Figure 1c. By
18420 sec UT (Figure 1d), the cigar shapes have been transformed into pancake
distributions and the counting rate begins to decrease. A negative bay in the
B - 26
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H-component recorded at Great Whale River begins at * 0508 UT * 18480 sec UT.
A series of chaotic distributions ensue but when the flux recovers at 18970
sec UT the distributions have clear cigar like characteristics at all energies
(Figure 1e). Eventually ( * 0530) pancakes form in the lowest four energy
channels, but cigar distributions remain in the highest energy channels
(Figure 1f). This situation obtains until the end of the film.
December 14, 1976 Event
This event is an example of an extremely quiet day. Before the start of
the film the IMF had a small southward component (in solar ecliptic coordi-
nates) for several hours. Auroral zone stations (Leirvogur in particular)
show essentially no geomagnetic activity. The three hour Kp values were:
December 14 (1+, 2+, 1", 1", 1", 0+, 0+, O and December 15 (0+, 1", 0+, 1+,
0, 0, 0+, 0). The movie starts at 2300 UT on December 14. There are no
discernable variations in the pitch angle distributions during the course of
the film. The lower energy channels all show very weak pancake distributions;
there are hints of a cigar distribution in the highest energy channel. Repre-
sentative frames are shown in Figures 2a and 2b for times near the beginning
and the end of this time interval.
September 2, 1976 Event
Prior to the start of the movie at 0300 UT, the B component (in solar
magnetospheric coordinates) had been nearly zero with small northward and
southward excursions. At 0300 UT the Great Whale magnetogram indicates a
substorm recovery was in progress. 1976-059 was near the midnight meridian.
The Cp parameter was decreasing, corresponding to an increasingly pancake-
shapecf distribution. 9p showed a slight decrease corresponding to a less
taillike configuration or the magnetic field. The azimuthal angle of the field
which had been 20° west was returning to 0° indicating a field lying in the
local meridian. At approximately 0338 UT the Cp parameter began to increase.
The B component, which had been strongly northward since ^ 0240 UT, showed no
change near this time. Plasma data from IMP-J shows a high speed stream
starts at about this time. The increase in C2 continues until a strong cigar
distribution develops just prior to a series of particle injections beginning
at x 0520 UT. A very large injection which reaches a saturated flux level
starts at 0545 UT [cf. Baker et al. (1978 ) for a discussion of the stable
trapping limit ( Kennel -Petschek limit) observed by our instruments]. A nega-
tive bay develops at Great Whale starting at s 0530 when the station was only
a few minutes past local midnight.
At the beginning of the movie (Figure 3a), the three lowest energy chan-
nels show a pancakelike distribution, the highest two channels show a weak
cigarlike distribution and the 95-300 keV channel is more or less isotropic.
By 0350 UT, well before the southward turning of the IMF, the highest four
channels show pancake distributions, the 45-300 keV channel has appreciably
flattened, and the 30-300 keV channel still retains the initial pancakelike
shape (Figure 3b). Within j» 25 minutes after the IMF is directed south, all
channels display cigarlike distributions (Figure 3c).
The cigarlike shapes become more accentuated as time progresses until *
0512 when the 30-300 keV channel recovers to an isotropic state (Figure 3d).
In the next five to six minutes all channels become pancakelike (Figure 3e) .
After the pancake shapes are well established the spin-averaged counting rate
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increases by a factor of four. This increase showed some evidence of energy
dispersion on a time scale of s 1 minute.
After the increase there were quasiperiodic oscillations of the spin-
averaged 30-300 keV electron flux with a period of ^ 5 minutes. However, the
higher energy channels show that there must have been a series of injections
since these peaks occur at earlier times in successively higher Channels. At
«r_0545 a large decrease occurs and a new cigar distribution is observed
(Figure 3f ) . The omnidirectional flux climbs to a quite high value in about
one half hour and slowly forms a pancake distribution at all energies (Figure
3g).
In summary, the magnetosphere seemed to be relaxing somewhat from 0300 to
0338 UT. At that time, before the field becomes directed southward, cigar
distributions begin to form. Pancakelike distributions reform a few minutes
before the first of a series of injections reach the spacecraft. A complex
series of events follow the first injection.
The formation of cigarlike distributions is in accord with our notion that
such distributions are indicators of stresses in the magnetosphere. In this
particular case, the stresses may have been induced by the high speed solar
stream and then increased when the IMF turned south. The change to pancake-
like distributions just prior to the large injection may have been due to
energy dispersion effects, adiabatic changes (the field direction did not
change at the time of the first injection) , or some form of wave-particle
interaction which isotropized the distribution. It should be noted that the
spacecraft is moving away from midnight where the pitch angle distribution is
usually most cigarlike.
August 4f 1Q76 Event
Prior to turning south at 2226 UT the IMF had been directed north for 5
hrs 19 min. There was a 16 min data gap starting at 1736 UT but the field was
strongly north before and after the gap. Before the gap there were a ten-
minute and a five-minute period when the field was at * 0° to the ecliptic.
At 2226 UT the field turned south for approximately 25 minutes, then remained
north for the duration of the film except for a few southward excursions.
(There is a data gap from 0132 to 0150 UT which is given as a straight line in
the movie.)
The pitch angle anisotropy was very pancakelike when 1976-059 was near
local noon ( + 1515-1615 UT) and, after a data gap, in the local time range
18-20 hr (' 2015-2215 UT). In fact the quiet time (K_i 1 +) anisotropy would
be more pancakelike only 10% of the time (Higbie et^Tl. 1978) compared with
data in the above local time intervals. After 2215 UT the anisotropy, began
to rise until it was above the 90% percentile line by 0000 UT on August 5.
The solar wind conditions showed no unusual changes during this period except
for an increase in the temperature by a factor of two at «/» 2230.
The movie starts (Figure 4a) with all energy channels showing well devel-
oped pancakelike distributions . Then distributions slowly flatten out with
the highest energy channels showing occasional weak cigarlike distributions.
By 2325 UT all channels show well developed cigar distributions which are most
accentuated at higher energies, e.g. the peak to valley ratio is 1.1 for the
B - 35
30-300 keV channel, but 2.8 for the 200-300 keV channel. There are two brief
dropouts in the spin-averaged flux at 2356 on 4 August and then at 0035 UT on
5 August and a weak enhancement at 0101 UT. The distributions remain reason-
ably well organized during the second dropout (Figure 4c) and during the
enhancement (Figure 4d) and demonstrate that they retain their cigarlike
character. Thus these three excursions may be due to boundary motion combined
with a radial gradient in the electron flux. The cigar shapes are well
established prior to the flux enhancement at 0147 UT. The cigar distributions
remain, despite the increased flux until 0157 UT when the 30-300 keV distribu-
tion becomes weakly pancakelike as illustrated in Figure 4e. This condition
persists for only three minutes before the flux returns to about the level
that had been established prior to 0147 UT and a cigarlike distribution is
established in the lowest energy channel. There is another increase at 0207
UT and a large injection at 0210 UT. The omnidirectional flux increases by a
factor of approximately eight during this injection. Well-formed pancakelike
distributions develop in the lowest three channels, but cigarlike distribu-
tions persist in the highest "two channels (Figure 4f ) . As the counting rate
slowly decreases over the next 45 minutes the cigar distributions slowly
reform until by the end of the movie all channels show cigars. During this
entire sequence the local field line direction, as determined from the sym-
metry axis of the distribution, changed very little. The colatitude was 40
in magnetic dipole coordinates at the start of the movie and increased to 50°
which implies that the field was quite stretched. The magnetogram at
Narssarssuaq shows several distinctive features during this period. A case
could be made for identifying all the flux dropouts and increases at 6.6 R„
except for the dropout at 2356 UT, with various rapid changes in the H compo-
nent displayed in the magnetogram.
To summarize, there are a number of flux enhancements and dropouts that do
not significantly change the basic cigarlike distributions observed. Thus
these changes may be due to boundary motions or local adiabatic effects only.
The flux injection at 0210 UT was accompanied by pancakelike distributions and
may thus reflect a true injection and reconfiguration of a portion of the
magnetosphere. No dramatic associations with parameter changes in the solar
wind were noted.
December 21 r 1Q76 Event
There was a data gap in the Imp J interplanetary field data from * 2230 UT
on 20 December to ^ 0100 UT on 21 December. During the period covered by the
movie the B component of the IMF was very weak (<. 2.5 y) and varied both
north and south. The plasma analyzer on Imp J showed a few minutes of cover-
age just after 0100 UT and continuous coverage after 0400 UT. The solar wind
speed was * 390 km/sec for both periods. Except for two samples of bad data
at 7770 sec and 8150 sec UT that were unfortunately not edited out of the
movie, the spin averaged counting rate shows essentially no variations.
Auroral zone magnetograms , Narssarssuaq in particular, show no substorms but
essentially flat traces. The pitch angle distributions are essentially
isotropic at all energies throughout the movie. Suggestions of pancake or
cigar shapes can be seen in individual frames and the loss cone is evident,
but no significant anisotropy is observed. Typical frames for the beginning
and end of this period are shown in Figure 5.
B - 36
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B - k]
DISCUSSION
Examples have been given illustrating a prediction technique for sub-
storms. A movie format was used which shows the low energy pitch angle dis-
tributions and their evolution in time for several energies. It is conceiv-
able that such distributions might be displayed in real time for the use of
ground personnel to monitor conditions at geostationary orbit". When the
spacecraft is in the correct interval of local time ( s 2000 to 0300 hours) the
character of the pitch angle distributions can be used to gauge the probabil-
ity of the occurence of a substorm. A limited number of copies of this film
are available for loan.
ACKNOWLEDGMENTS
We express our appreciation to Drs . R. Lepping and N. F. Ness for the
use of the flux gate magnetometer data from Imp-J obtained through the
National Space Science Data Center. Our particular thanks goes to Patricia A.
Max who ran the computer codes. This work was performed under the auspices of
the U.S. Department of Energy.
REFERENCES
Baker, D. N. , P. R. Higbie, E. W. Hones, Jr., and R. D. Belian (1978a): High
resolution energetic particle measurements at 6.6 R-, 3i low-energy elec-
tron anisotropics and short-term substorm predictions, J . Geophys. Res. ,
(in press) .
Baker, D. N., E. W. Hones, Jr., P. R. Higbie, R. D. Belian, and P. Stanning
(1978b): A correlation study of > 30 keV electrons at 6.6 R£ with high
latitude riometer measurements. The AGU Chapman Conference on Magneto-
spheric Substorms and Related Plasma Processes, Los Alamos.
Bogott , F. H. and F. S. Mozer (1971): Equatorial proton and electron angular
distributions in the loss cone and at large angles. J . Geophys. Res. ,
76:6790.
Burton, R. K. , R. L. McPherron, and C. T. Russell (1975): An empirical
relationship between interplanetary conditions and Dst . J . Geophys. Res. ,
80:4204.
Caan, M. N., R. L. McPherron, and C. T. Russell (1977): Characteristics of
the association between the interplanetary magnetic field and substorms,
J. Geophys. Res. , 82:4837.
Higbie, P. R. and W. R. Moomey (1977): Pitch angle measurements from satel-
lites using particle telescopes with multiple view directions. Nucl.
Instru. and Meth. , 146:439.
Higbie, P. R., D. N. Baker, E. W. Hones, Jr., and R. D. Belian (1978): Pitch
angle distributions of > 30 keV electrons at geostationary altitudes.
AGU Chapman Conference on Quantitative Modeling of Magnetospheric
Processes, La Jolla.
B - 42
Higbie, P. R., R. D. Belian, and D. N. Baker (1978): High-resolution energetic
particle measurements at 6.6 RE, 1, electron micropulsations . J. Geophys.
Res. , ( in press) .
Hirshberg, J. and D. S. Colburn (1969): Interplanetary field and geomagnetic
variations - a unified view. Planet. Space Sci. , 17:1183.
Kamide, Y. , P. D. Perreault, S. I. Akasofu, and J. D. Winningham (1977):
Dependence of substorm occurrence probability on the interplanetary
magnetic field and on the size of the auroral oval. J. Geophys. Res. ,
82:5521.
Kamide, Y. and S. Matsuskita (1978): A unified view of substorm sequences. J.
Geophys. Res. , 83:2103.
Kaye, S. M., C. S. Lin, G. K. Parks, and J. R. Winckler (1978): Adiabatic
modulation of equatorial pitch angle anisotropy. J . Geophys . Res. ,
83:2675.
Kokubun, S. , R. L. McPherron, and C. T. Russell (1977): Triggering of
substorms by solar wind discontinuities. J . Geophys. Res. , 82:74.
McPherron, R. L. (1970): Growth phase of magnetospheric substorms. J. Geophys.
Res., 75:5592.
Parks, G. K. , G. Laval, R. Pellat (1972): Behavior of outer radiation zone and
a new model of magnetospheric substorm. Planet Space Sci , 20:1391.
Perreault, P. D. and Y. Kamide (1976): A dusk-dawn asymmetry in the response
of the magnetosphere to the IMF B component. J . Geophys. Res. , 81:4773
Pfitzer, K. A., T. W. Lezniak, and J. R. Winckler (1969): Experimental
verification of drift-shell splitting in the distorted magnetosphere. J .
Geophys. Res., 74:4687.
Roederer, J. G. (1972): Geomagnetic field distortionns and their effects on
radiation belt particles. Rev. Geophys. Space Phys. , 10:599.
Svalgaard, L. (1977): Geomagnetic activity: dependence on solar wind
parameters. Coronal Holes and High Speed Streams, J. B. Zinker, ed. ,
Colorado Associated University Press, 371-441.
B - 43
PREDICTING PARTIAL RING CURRENT DEVELOPMENT
C. Robert Clauer and R. L. McPherron
University of California, Los Angeles
Institute of Geophysics and Planetary Physics
Los Angeles, California 9002 A
Analysis of midlatitude ground magneto grams during periods of
substorm activity reveals that some substorms are associated with a large
decrease in the northward (X) component of the geomagnetic field near
dusk but that many other substorms are not. The dusk depression of the
field is interpreted as the magnetic signature of the asymmetric (or
partial) ring current. The development and decay of the partial ring
current is shown to be strongly dependent on the B„ (northward) com-
ponent of the interplanetary magnetic field (IMF) . The partial ring
current develops only during periods of sustained southward IMF of
several gammas or greater. A subsequent change to northward IMF will be
followed by a rapid (two or three hour) decay of partial ring current.
Thus, measurements in the IMF can be used to predict the development and
decay of the partial ring current. It may eventually be possible to
infer the solar wind electric field based on partial ring current para-
meters. This method of inference would lend itself to real time moni-
toring using a worldwide chain of midlatitude observatories similar to
the partial chain established for the IMS. In general, midlatitude
data coverage is more complete than coverage at high latitudes. The use
of this more complete data set to monitor the development of the partial
ring current offers greater sensitivity than obtained with the D„ index
and may eventually prove more reliable than high latitude indices for
monitoring the IMF.
I . INTRODUCTION
The southward component of the interplanetary magnetic field (IMF)
has been shown to exhibit a fundamental relationship with geomagnetic
activity (Hirshberg and Colburn, 1969). The high correlation between
IMF orientation and geomagnetic activity has generally been regarded as
confirmation of the open magnetospheric model introduced by Dungey
(1961) . In the open model of the solar wind-magnetosphere interaction,
the strength of the electrostatic field imposed across the magnetosphere
is proportional to the dawn-dusk component of the interplanetary elec-
tric field (IEF) . The IEF depends upon the solar wind velocity V and
the IMF through the relation j§= - ^ X B^. A southward component of the
IMF gives rise to a dawn to dusk component of the IEF.
B - kk
Recently, much effort has been directed toward improving our
understanding of the effects of the potential drop imposed across the
magnetosphere by its interaction with the solar wind. The suggestion
was made by Dungey (1961) and concurrently by Axford and Hines (1961)
that geomagnetic activity was directly related to plasma convection.
In general, plasma in the magnetosphere is convected by two processes.
The most spatially uniform and temporarily stable component of the
convection is driven by the externally imposed electrostatic field
while a more intense and localized component is thought to result from
the induced electric fields produced during substorm expansions. This
second component of the convection, substorm expansions, has generally
been considered the principle mechanism by which plasma is energized
and transported to the inner magnetosphere to form the ring current
(Davis and Parthasarathy 1967, Davis 1969).
The results which are presented in this report indicate that the
development of the partial ring current is more closely related to the
IMF and, therefore, to the strength of the electrostatic field than to
individual substorms. This result suggests a direction for prediction
research. In particular, it may be possible to infer conditions in the
solar wind using ground determined partial ring current parameters.
Alternatively, measurements of the. IEF could be used to predict the
development and decay of the partial and symmetric ring currents.
II.
EXPERIMENTAL RESULTS
The magnetic signatures of the symmetric and partial ring currents
are best observed with midlatitude ground magnetic observations. Using
a worldwide network of observatories, one can observe the spatial and
temporal development of these large scale current systems (Troshichev
and Feldstein, (1972), Clauer and McPherron, (1978).
Figure 1 is a schematic illustration of a very simple model of the
partial ring current system and substorm expansion phase current system
having field aligned closure through the eastward and westward electro-
jets respectively. The magnetic effect of these currents at midlatitudes
as a function of the local time or position around the earth is illus-
trated at the top of the figure. The X or northward component of the
field is depressed by the partial ring current and enhanced by the sub-
storm expansion current. The Y or eastward component is enhanced in
regions of outward field aligned current and decreased in regions of
earthward field aligned current. A number of parameters which charac-
terize these current systems may be obtained from the local time
magnetic perturbation profile. They include the magnitude of the
disturbance, the extent and the central meridian.
To compute these profiles, we use digital data from a chain of mid-
latitude magnetic observatories, listed in Table 1. The average quiet
B
hb
MIDLATITUDE LOCAL TIME PROFILE PARAMETERIZATION
Field Aligned Currents
In
h
Out
In
H
Partial Ring Current Substorm Expansion
Current
Central
Meridian
Magnitude
I ■ I I I L
Magnitude
Extent
SIZE = Magnitude x Extent
■ i i i i
12
18 00 06
Local Time (hours)
12
Equatorial Projection of Inferred Currents
Figure 1. Schematic representation of local time magnetic perturbation
profile due to simple wire model substorm expansion phase current
and partial ring current with field aligned closure through the
auroral electrojets AX is the perturbation in the northward
component, AY is the perturbation in the eastward component
B - ke
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B - 47
day field, which includes diurnal, seasonal and secular variations, is
removed from the data and a smooth profile is fitted through the result
using cubic splines.
Successive local time profiles are computed at 2.5 minute intervals,
in Universal Time and the result is displayed in the form of Local Time -
Universal Time (LT - UT) contour maps. These maps display the temporal
and spatial development of magnetic disturbances. We also compute para-
meters which characterize the successive profiles. These include the
maximum and minimum value of magnetic perturbation, D{,T the worldwide
average midlatitude perturbation, the asymmetry defined as the difference
between the maximum and minimum perturbations. We will illustrate our
results and the mapping procedure with two examples.
Figure 2 shows the high latitude activity on Feb. 11, 1967, a day
characterized by a large isolated substorm. It was quiet prior to 0515
UT at which time a substorm onset occurred. Local midnight at each
station is indicated by a cross above the trace. Table 2 gives the
station locations.
Figure 3 shows the midlatitude observations along with the inter-
planetary data. The center panel is a LT-UT map of the magnetic distur-
bance in the X component. The vertical axis is local time or position
around the earth relative to the earth-sun line. Local midnight is at the
center and local noon at the top and the bottom edges. Contours of the
magnetic deviation from a quiet day are drawn at 5y intervals. A
vertical line is drawn at 0515 UT. The average field prior to 0515 was -
10y and contours above that level have been shaded. A positive field
enhancement centered near 0300 LT begins at 0515 UT and is the signature
of the substorm expansion. A simultaneous depression in the field
develops near dusk. This is the partial ring current signature.
Parameters derived from the mapping procedure are plotted in the
bottom panel. The top three traces are the maximum, average (D ) , and
minimum midlatitude, field perturbation. There is a clear increase in
the maximum due to the substorm while the minimum decreases as a result of
the partial ring current. The bottom three traces are the asymmetry index
defined as the difference between the maximum and minimum, and the local
time position of the maximum and minimum.
The top panel displays the solar wind density and velocity and the
north-south component of the IMF (B„) in solar magnetospheric coordinates.
The data gap in the density and velocity measurements is partially filled
in with hourly average values from the interplanetary medium data book
by King (1977)1 Note that the partial ring current indicated by the de-
pression of the minimum continues to develop during the substorm recovery
indicated by a decrease of the maximum. The development of the partial
ring current is occurring during a period of sustained southward B„. A
vertical line is drawn at the onset of partial ring current decay. Note
that the decay follows the northward turning of B .
B - kQ
\400y
HIGH LATITUDE MAGNETOGRAMS
H-COMPONENT
February 11, 1967
WDC-A Geomagnetic Data
Processed and plotted by
UCLA IGPP
10 12 14 16 18 20 22 24
Universal Time
Figure 2. High latitude raagnetograms of H component for Feb. 11, 1967.
Vertical line at 0515 UT marks substorm onset. Cross above trace
marks local midnight at observatory.
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g. -5H
o^^V,
"T"
^1
r700 x~
600 u £
-500 "5)^
400 >^
'J^V^LYA^^r^1,J,^^'
0515
Universal Time (hours)
Figure 3. Interplanetary data and midlatitude ground data for Feb. 11, 1967
(From top to bottom) Solar wind proton number density, solar wind
velocity, north-south component of interplanetary magnetic field
(southward field is shaded), LT - UT map of magnetic perturbations
measured in north-south component of midlatitude field and parameters
of the midlatitude disturbance: AX , DcT> AX • „ , asymmetry, local
max 91 miii * J
time position of AX and local time position ot AX„. . Vertical
max , . min
lines mark substorm onset (0515UT) and onset of partial ring current
decay (0835UT) .
B - 5
Figure 4 shows the high latitude activity for Jan. 23, 1968, a day
characterized by a small amount of activity early in the day culminating
with a large substorm having an onset at 20 UT. Figure 5 shows the solar
wind and midlatitude ground observations. The activity during the earlier
part of the day was small and did not result in any large midlatitude
disturbance. The substorm at 20 UT, however, is comparable in size to the
substorm on Feb. 11. Little, if any, partial ring current development is
shown either on the map or by the midlatitude minimum parameter. A dif-
ference between this event and the one on Feb. 11 can be seen in the
character of the B component of the IMF. For this event the field was
fluctuating north and south for short periods of time.
Of the twenty-five events examined thus far, 5 events had clear large
southward turnings of the IMF associated with the development of a distinct
partial ring current. In each case, when the IMF turned northward, decay
of the partial ring current was observed.
It appears that two classes of substorm activity are distinguishable
using midlatitude magnetic observations - substorms associated with clear
large partial ring currents and substorms associated with little or no
partial ring current magnetic signature. Figure 6 shows superposed epoch
averages of the midlatitude parameters and B timed relative to the sub-
storm onset for the two groups of events. The average local time position
of the maximum and minimum is also shown. The panel on the left presents
the results for substorms in which the dusk depression was less than the
noise level due to S variability. At dusk this level is about 15y (Clauer,
McPherron and Kivels8n, 1979) . There is a small depression of the minimum
associated with the substorm, however, it is probably the result of the
substorm associated Birkland currents since it is very close to the sub-
storm maximum and slightly to the east. The B component averages about
3y prior to the substorm.
The panel on the right shows the results for substorms associated
with clear partial ring current signatures. Each of these events was
associated with a decrease of the dusk field of more than 20y. The events
followed a large southward turning by about 1 hour. The partial ring
current measured by the minimum begins to develop about 15 minutes after
the southward turning and 45 minutes before the substorm. The substorm
position appears to be centered near 0400 LT while the partial ring current
center is 2100 LT one hour after the substorm onset.
Figure 7 shows further analysis of the events which had well defined
partial ring currents. In the left panel the superposed averages were
timed relative to the onset of the partial ring current development. The
B„ component reached - 4y 30 minutes before the onset time and remained
substantially southward. The panel on the right shows the averages super-
posed relative to the onset of partial ring current decay. The decay
begins shortly after the B„ component reaches -2.5y.
B - 52
HIGH LATITUDE MAGNETOGRAMS
H-COMPONENT
[40°r January 23, 1968
4. 1
LR 12085
NAS m5
GWR 9832
^C 6969
ME 13192
15751
cz - ~ 12898 -f
BW 97l2
UE 14113
CC 3395
DI 6405
* SI
E CO
o
-v>/,-«t*"
WDC-A Geomagnetic Data
Processed and plotted by
UCLA IGPP
0 2 4 6 8 10 12 14 16 18 20 22 24
Universal Time
Figure A. High latitude magnetograms of H component for Jan. 23, 1968.
Vertical line at 2000 UT marks substorm onset.
B - 53
<
d
CO
10
January 23, 1968
1 — 1 — 1 — 1 — 1 — t — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1 — 1— 1 — 1 — p
-1 — 1 — 1 — 1 — r
I ' ' ' '
>v./<v jr*/**- '^v
'*,
/^v^r
10 n
5:
Ih \ffH" '• **•**■&
'-V...A ^^.^
— — ^
v,/-> j-^/Uva^Vw^
A^'N*^
^JhJITHLft
<j y f T
rl"»| wN"
■^^^•W^-^V** -
r700 >—
- 600 • g «
- 500-55 F
L400>t*
^^^^,/Y^T^KjfVlv»^
«/•
— Max Dusk
^ 12 J
|_J Dawn"
Min Dusk-
8 12 16
Universal Time (hours)
1 1 1 — 1 — r-» — r
24
Figure 5.. Interplanetary data and midlatitude ground data for Jan. 23, 1968.
Format is the same as Figure 3. Vertical line at 2000 UT marks substorm
onset.
B - $k
SUPERPOSED EPOCH AVERAGES
CO
CL
LU
I-
LU
<
<
Q_
Q
Z
Z)
O
cc
O
LU
Q
D
5
Q
2
SUBSTORM
Without Partial Ring Current
10 Events
T
ONSETS
With Partial Ring Current
8 Events
0 000 0
y 00-
EPOCH
Figure 6. Superposed epoch averages of parameters timed relative to sub-
storm onset for events with little or no partial ring current (left)
and events with a clear large partial ring current (right). Para-
meters are (from top to bottom) north south component of inter-
planetary magnetic field, AX^^ DST, AXm±n and asymmetry. Clocks
indicate average local time position of AXmax and AXmin during epoch,
B - 55
SUPERPOSED EPOCH AVERAGES
10 Events
Partial Ring Current
Development
Partial Ring Current
Decay
LL
CO
cc
LU
t-
LU
<
CC
<
a.
O
DC
O
LU
O
3
<
_l
Q
EPOCH
Figure 7. Superposed epoch averages of parameters of events with distinct
large partial ring currents. Epoch averages are timed relative to the
onset of partial ring current development (left) and onset of partial
ring current decay (right). The format is the same as Figure 6.
B - 56
CONCLUSIONS
Among the principal goals of magnetospheric research are to develop
methods which can use ground based measurements to monitor the conditions
in space and develop parameters which can predict magnetospheric activity.
Burton, et al., 1975, developed an empirical relationship using the solar
wind electric field and dynamic pressure which predicted the development
and decay of the symmetric ring current measured by the D index. The
prediced and measured D values were extremely similar for several storms
tested. From Figure 3 xt is clear that the midlatitude minimum index is
more responsive to smaller events than D . There is also sufficient
evidence to suggest that it may be possible to develop a relation between
the midlatitude minimum and solar wind parameters similar to the Burton
result but with the advantage of greater sensitivity. Inversion of the
relationship would permit midlatitude magnetic parameters to act as moni-
tors of the solar wind electric field.
The use of midlatitude data as a real time diagnostic tool for the
magnetosphere has several advantages over similar use of auroral zone and
polar cap data. Real time data acquisition using synchronous satellites
offers better reliability over the tenuous radio or telephone data links
at high latitudes, particularly during disturbed conditions. Operation
of midlatitude observatories in general tends to be easier than operation
of stations in remote areas of the arctic. The important result of this
is a more complete data base at midlatitudes. As our understanding of
the physics of the dynamical processes of the solar-magnetospheric inter-
action develops, the use of midlatitude geomagnetic data as a diagnostic
and predictive tool will become more important.
ACKNOWLEDGEMENTS
This research has been supported by the Office of Naval Research
through grant N00014-75-C-0396. We thank the World Data Center A for sup-
plying the digital ground magnetograms and C. P. Sonett and D. S. Colbrun
for supplying the Explorer 33, 35 magnetic field data.
REFERENCES
Axford, W.I. and CO. Hines (1961): A unifying theory of high latitude
geophysical phenomena and geomagnetic storms. Can. J. Phys . ,
39: 1433.
Burton, R.K., R.L. McPherron and C.I. Russell (1975): An empirical
relationship between interpL
J. Geophys. Res., 80: 4204.
relationship between interplanetary conditions and D
Clauer, C.R. and R.L. McPherron (1978): On the relationship of the partial
ring current to substorms and the IMF, J. Geomag. Geoelect., 30: 195.
B - 57
REFERENCES (Cont.)
Clauer, C.R., R.L. McPherron and M.G. Kivelson (1979): How does the vari-
ability of Sq currents affect midlatitude determination of ring
current development, to be presented at 1979 spring AGU meeting,
Washington, D.C.
Davis, T.N. and R. Parthasarathy (1967): The relationship between polar
magnetic activity DP and growth of the geomagnetic ring current,
J. Geophys. Res., 72: 5825.
Davis, T.N. (1969): Temporal behavior of energy injection into the
geomagnetic ring current, J. Geophys. Res., 74: 6266.
Dungey, J.W. (1961): Interplanetary magnetic field and the auroral zone,
Phys. Rev. Lett., 6: 47.
King, J.H. (1977): Interplanetary medium data book - appendix, National
Space Science Data Center, NASA, GSFC, Greenbelt, Md. 20771
Troshichev, O.A. and Ya I. Feldstein (1972): The ring current in the
magnetosphere and polar magnetic substorms, J. Atm. Terr . -Phys . ,
34: 845.
B - 58
ON THE PREDICTABILITY OF RADIATION BELT ELECTRON PRECIPITATION
INTO THE EARTH'S ATMOSPHERE FOLLOWING MAGNETIC STORMS
Walther N. Spjeldvik and Lawrence R. Lyons
NOAA/ERL, Space Environment Laboratory
Boulder, Colorado 80303, USA
The earth's radiation belts are subject to drastic structural
changes during magnetic storms. Fluxes of energetic electrons at
hundreds of keV are increased by orders of magnitude during the
storm main phase. During the recovery phase the trapped fluxes de-
cay back to quiet time levels by precipitating the excess electrons
into the middle latitude atmosphere where they profoundly enhance
the ionization rates in the D and E regions. The present report em-
phasizes the operating physical mechanism and seeks to establish a
preliminary prediction scheme based on causal interrelations rather
than purely statistical correlations. Although it is possible to
make an order-of-magn i tude prediction for the disturbed period fol-
lowing magnetic storms, more detailed work is needed to develop a
precise quantitative forecast. In particular, greater emphasis on
the source and distributions of plasmaspher ic ELF whistler mode wave
turbulence (hiss) is called for. The predictions of the ionospheric
electron density enhancements may be used to forecast VLF to MF
ionospheric radio wave propagation disturbances.
1. INTRODUCTION
It has long been established that the D and E regions of the
earth's ionosphere become severely disturbed following the onset
of major magnetic storms (e.g. Lauter and Knuth, 1967; Belrose and
Thomas, 1 968) . During such times the lower ionosphere exhibits en-
hanced absorption of LF and MF (^ 0.2 MHz) radio waves that
reflect from the E-layer, and lower frequency waves that reflect
from D-region heights (^ 80 km) show substantial phase disturbances
generally with significant phase advance during the post storm
events (Belrose and Thomas, 1 968) - In a recent work Lauter et al .
(1977) have found that the post storm absorption events occur rather
simultaneously in both hemispheres on subauroral latitudes down to
^ 50 geomagnetic latitude. In contrast they found that D-region
absorption enhancements during the main phase of magnetic storms
can show strong transient latitudinal dependence.
This difference between the post storm and main phase absorp-
tion enhancements may be qualitatively understood in terms of storm-
time displacement of the plasmapause. During the storm main phase
enhancements of the dawn-to-dusk convection electric field makes
B - 59
the plasmasphere shrink to a size where middle latitude geomag-
netic field lines (l_ ^ 3_5 or A ^ 50-65°) can map outside the plasma-
sphere. Any wave-particle interaction induced electron precipita-
tion under such conditions is likely to be highly transient, perhaps
in analogy with auroral characteristics. As the main phase of the
storm subsides, the plasmasphere starts to recover and extends to-
wards higher invariant latitudes. Thus the post storm middle lati-
tude ionospheric effects map along magnetic field lines within the
high density plasmasphere where plasma wave propagation and wave-
particle resonance conditions are quite different from the conditions
outside. It has been found that the plasmapause separates the
region of intermittent ELF chorus emissions beyond the plasmasphere
and the quasi-steady ELF broadband (0.1-1 KHz) whistler mode hiss
within the plasmasphere (e.g. Thorne et al., 1973).
The D-region effects associated with the recovery phase of mag-
netic storms are found to be caused by radiation belt electron
precipitation (e.g. Spjeldvik and Thorne, 1975a, b, 1976). There
are other known classes of D-region disturbances. X-ray solar
flares can cause Sudden Ionospheric Disturbance (SID) events and
solar proton emissions can give rise to Polar Cap Absorption (PCA)
at latitudes sometimes extending well southward of the auroral
zone. Predictions of such occurrences must come from solar physics
(e.g. Krivsky, 1977) and is beyond the scope of this report.
A catalog of D-region absorption presented as daily averages for
the period 19^8-1976 is now available (Lauter, 1977). In this
paper we will concentrate on the post storm ionospheric disturb-
ances associated with the electron precipitation.
A practical application of prediction of these storm after-ef-
fects stems from the fact that the enhanced energetic electron pre-
cipitation is durable over time scales of days. Since some naval
navigation systems utilize VLF wave propagation properties, it is
conceivable that severe and persistent ionospheric modification
leading to significant VLF phase advances may, if not corrected for,
lead to mi snavigat ion.
2. RADIATON BELT ELECTRONS
It is clear that the observed ionospheric radio wave absorption
and phase effects may be explained in terms of an enhanced D and E
region free electron concentration. The physical mechanisms re-
sponsible for ionization by precipitating energetic electrons have
been studied extensively in recent years. Thorne et al. (1973)
have presented observations showing that a class of ELF whistler
mode wave turbulence, known as pi asmaspher i c hiss, in the frequency
range 0.1 to 1 kHz exhibits a fairly persistent substantial inten-
sity level of tens of milligammas on L-shells below the plasma-
pause location.
B - 60
Lyons et al. (1971, 1972) used such hiss observations within
the plasmasphere to model the efficiency of radiation belt electron-
plasmaspher ic hiss interaction for energetic electrons at 20 keV to
2 MeV. In a subsequent paper Lyons and Thorne (1973) demonstrated
that the radial structure of the earth's quiet time electron belts
can be understood in terms of inward radial diffusion from an outer
zone electron source and losses due to pitch angle scattering into
the atmospheric bounce loss cone. Their most significant result
was the unambiguous explanation of the separation of the two Van
Allen radiation zones of energetic electrons.
The quiet time, storm time and post storm morphology of ener-
getic radiation belt electrons within the location of the quiet
time plasmapause (L ^ 5) is illustrated in Figures 1 and 2 (from
Lyons and Williams, 1975). The data shown are from Explorer 45 and
include the geomagnetic storm period in December 1971. Figure 1
gives the radial profiles; notice the pronounced quiet time "slot"
region located just beyond L = 3 (dashed lines). With the onset
of the storm the slot region becomes filled with freshly injected
electrons (orbit 101 in Figure 1), and during the storm recovery
phase the fluxes decay down to the normal quiet time two-zone struc-
ture. The progress of the observed decay is shown as the electron
Indicoted Orbit
20 51 . U»
20 05
ORBIT-98.DEC 16
35-70 MV («lb«wid)
J i ry. i i L
-Orbit 94, Dec 15 (tor reference)
r30 8-59 505
ORBIT 106, DEC 19
ORBIT 112. DEC 21
2141 1114
2023 Oil
0 53 UT
ORBIT ISO. DEC 27
Figure 1. Observed radial profiles of the perpendicular (90°
local pitch angle) electron flux obtained near the geomagnetic
equator for the periods preceding, during and following the storm
of December 17, 1971. Solid curves give the profiles from the
orbit indicated in each panel, and the dashed curves give the pre-
storm profiles from orbit 94 outbound (December 15, 1971) for com-
parison. To clearly display the data, the 120-240 keV, 75-125 keV,
and 35-70 keV fluxes have been multiplied by 101, 10 2, and 103, re-
spectively. Note the relaxation of the post-storm profiles to
their pre-storm shapes and intensities.
flux versus time in Figure 2. Notice that at high L-shells (L £ 5)
injections, possibly by substorm activity, take place during the re-
covery phase. On lower L-shells a rather clear cut decay following
the main phase injection is seen. On very low L-shells in the in-
ner radiation zone, L % 2, the electron fluxes are seen to be very
stable, presumably because the main phase injection did not reach
this close to the earth.
DECEMBER 1971 I JAN 197? Elec
17 21 2b
35-70
120-240 10'
240-560 10°
Figure 2. Fluxes of equatorially mirroring electrons versus uni-
versal time for the period Dec. 9, 1971-Jan. 9, 1972. All availa-
ble data points from both inbound and outbound portions of the Ex-
plorer *+5 are shown. Each panel shows the observations at the indi-
cated L-value for the four energy channels. The 120-2^0 keV , 75-125
keV, and 3 5~70 keV fluxes have been multiplied by 101, 1 02 , 1 03 ,
respectively. Dst is also shown.
B - 62
3. ELECTRON SCATTERING
Plasmaspher ic hiss can resonate with energetic radiation belt
electrons when:
co = k. . v. . - nfi
(0
where go is the plasma wave frequency, k and v.. are the components
of the wave propagation vector parallel to the local magnetic field
direction, Q is the electron cyclotron frequency and n is an integer
(n = 0, ± 1, ±2, ±3, ...)• Measurements have shown that the ELF
hiss exists almost continuously throughout the plasmasphere (e.g.
Russell et al., 1969; Thorne et al., 1973; Parady and Cah ill, 1973;
Smith et al., 1972*; Parady et al., 1975). The waves frequently ex-
hibit a sharp lower frequency cut-off near 100 to 200 Hz, a more
diffuse upper-frequency cut-off located near 1 kHz and a well-de-
fined maximum intensity at a few hundred Hz. During quiet time the
wide band average wave amplitude range from ^ 3 my to ^ 60 my, and
the wave intensity is increased during the recovery phase of a
magnetic storm (Parady et al., 1975; Smith et al., 197^) ; this is
illustrated in Figure 3-
The waves are always found to be highly turbulent with wave
energy distributed over all wave normal angles with respect to the
magnetic field. Since these waves can propagate obliquely to the
magnetic field, they are most frequently found to be distributed
throughout the plasmasphere (Thorne et al., 1973)- Indeed the ELF
45
30
QUIET
~|
15
1
n
1
45
30
15
0
STORM
INITIAL AND
i
MAIN PHASF
,__ H
i
1
-8 0
-6 0
STORM
RECOVERY
PHASE
-4 0
-3 0
LOGARITHM PEAK POWER, y /Hz
Figure 3- Histograms of peak spectral power during various phases
of magnetic storms deduced from 0G0-6 observations (from Smith
et al., 197^)- A definite intensification during the storm
recovery phase is seen.
B - 63
hiss appears to be the predominant wave mode within the plasma-
sphere. Current theories consider the plasmaspher ic hiss to be gen-
erated in the plasmapause region by ring current energy (tens of keV)
outer zone electrons penetrating into the plasmasphere (Lyons et al.,
1972; Thorne et al., 1973; Thorne and Barfield, 1976). Once gener-
ated, these waves, because of their low frequencies, undergo a near-
ly perfect reflection within the magnetosphere so that little wave
energy is lost to the earth's ionosphere (e.g. Kimura, 1966; Thorne
and Kennel, 1967).
Substorm associated variations in the ELF hiss are known to
occur (Thorne and Barfield, 1976), however, sufficient analysis to
allow forecast of such variability has not yet been accomplished.
On the other hand, a well defined perturbation of the plasmaspher ic
hiss has been found to occur during the recovery phase of magnetic
storms. Figure 3, which is taken from Smith et al . (197*0 clearly
demonstrates that the hiss is highly intensified at such times and
Smith et al. (197*0 found that this intensity remains high during
most of the post storm recovery phase. In contrast, there is little
difference between the hiss intensities during quiet times and during
the magnetic storm main phase. The post storm ELF amplitude increase
is typically a factor of three or four and this corresponds to over
an order of magnitude increase in the wave energy.
Using the observed properties of the plasmaspher ic hiss, Lyons
et al. (1972) calculated the lifetimes for radiation belt electrons
at energies which can resonate with the waves (20 keV to 2 MeV).
Some of their results for an assumed wave amplitude of 35 my are
shown in Figure *t; here a wave intensity maximum at 600 Hz is used
o
5 10'
o
10°
10-
1 1
\ I 2.0 MeV//
\ \ /
\ X
V
\ \y'\ ' ° MeV-'"
\\ \\
V \ 500 KeV .
-
200Ke\Nv A \
wm= 6OOH2
\\ "~~— -
Soj = 300Hz
Bwove = 35my
50KeV\\
N(L=4)= 1000 cm" J
20 KeV
2 3
L- VALUE
Figure k. Theoretical electron precipitation lifetimes versus L-
value for a range of electron energies: 20 keV to 2 MeV. The re-
sults are valid within the plasmasphere (from Lyons et al., 1972)
B - Gk
together with an effective bandwidth of 300 Hz. It should be noted
that these electron precipitation lifetimes are proportional to the
square of the wave amplitude and therefore scale with the wave in-
tensity such that
m
tp = V '-) <2>
where B is the nominal value of the average wave amplitude at
which the lifetimes T are qiven as function of enerqy and L-shell.
Ro _
trapped electron spectrum the rates of ener-
getic electron precipitation scale inversely with t (for details,
see Lyons and Thorne, 1971, 1972, and for applications see Spjeldvik
and Thorne, 1975a, b) .
Notice that for all electron energies there exists a relatively
sharply defined L-shell below which these lifetimes become very long
This marks the outer edge of the stable inner radiation zone and is
effectively a separator between the wave-particle interaction domi-
nated outer electron belt and the Coulomb collision controlled inner
belt. From Figure ^ we see that this boundary moves to higher L-
shells with decreasing electron energy, and this accounts for the
observed fact that the inner zone extends to higher L-shells with
decreasing electron energy. Using radiation belt electron data
Lyons et al . (1972) also demonstrated that the wave particle scatter
ing into the atmospheric bounce loss cone accounts for the post
storm decay of the radiation belts as function of L-shell and
electron energy beyond the inner radiation zone.
k. ENERGY DEPOSITION IN THE ATMOSPHERE
Once pitch angle scattering of energetic radiation belt elec-
trons has lowered the electron pitch angle to the immediate vicin-
ity of the atmospheric bounce loss cone, the electrons encounter
the denser parts of the earth's atmosphere within the next half
bounce period. Let a. (E) be the (energy dependent) nominal loss
cone angle defined such that an incident electron with equatorial
pitch angle a = a has 50% or more probability that its kinetic
energy will be degraded to 1 /e of its incident energy during the
next atmospheric encounter. The equatorial pitch angle range of
the loss cone spans only a small fraction of pitch angle space, at
I = k typically from 0° to 5.5° giving a total loss cone of ^ 11°.
The idealized case of isotropic electron precipitation has been
studied by Potema and Zmuda (1970) and Potemra (1973). However,
during the storm recovery phase the radiation belt electron pitch
angle diffusion rate practically always remains below the strong
diffusion limit (e.g. Lyons et al . , 1972; Spjeldvik and Thorne,
1975a). As a consequence the loss cone will exhibit the charac-
teristics of a steep down-step from the trapped flux level (a_ > a.. )
to the precipitated flux level (an a, a ). The fine details of the
narrow transition reg ion have been studied (Spjeldvik and Thorne,
1975a; Davidson and Walt, 1977) but some controversy still remains
B - 65
as to the preciseness of the analytical and numerical approxima-
tions (Spjeldvik, 1977; Walt and Davidson, 1978; Spjeldvik, 1978).
Fortunately, such details are not of great importance for the
height distributions of the energy deposited in the atmosphere by
the energetic electrons. An electron losing 1-1/e or more of its
incident kinetic energy is also so substantially scattered by the
atmosphere that practically all "memory" of the incident pitch
angle becomes lost. At radiation belt energies the backscattered
electron flux may be in the range 10-30% of the incident flux,
depending on energy (e.g. Spjeldvik and Thorne, 1975a; Davidson and
Walt, 1977). The major portion of the precipitated (an % a-. )
flux becomes stopped in the atmosphere, and in the process trie
incident electron energy is deposited as local excitation and
ionization of the atmospheric constituents and, at several MeV and
above, also in the generation of Bremsstrahl ung X-rays. Although
13 eV energy is sufficient to ionize an atmospheric molecule,
energy absorption by bound electron excitation makes an average of
35 eV necessary to produce a free ion-electron pair in air. Thus,
as a rule of thumb a 350 keV precipitated electron produces 10,000
ion-electron pairs along its trajectory. It is the magnitude and
height distribution of this precipitation source that is of prime
concern. A numerical code for simulating the energy deposition has
been developed by Walt et al. (1968) and has been applied by
Spjeldvik and Thorne (1975a) and by Davidson and Walt (1977) where
details can be found. Further analysis of the associated VLF
ionospheric wave propagation has been made by Larsen et al. (1976,
1977) and by Davis (1976) .
Figure 5 gives an example of the calculated ionospheric ion-
electron pair production rates due to energetic radiation belt
electron precipitation on September 6, 1966 using trapped electron
measurements made with the OV3~3 satellite early in the recovery
phase of a major magnetic storm. These results which are taken
from Spjeldvik and Thorne (1975a) are given for a wide range of ELF
intensities; the most probable post storm wave amplitudes are in
the range 30-60 my although intens i f icat ion to hundreds of my may
occur.
5. PREDICTABILITY OF THE ELECTRON PRECIPITATION
In the present context there are three levels at which fore-
casts of post storm energetic electron precipitation into the
atmosphere may be made:
(1) Qualitative assessment of the size and timing of the
ionospheric storm after-effects.
(2) Semiquantitative predictions of the overall magnitude and
temporal evolution with a probable error better than an
order of magnitude.
(3) Precise quantitative forecasts of the precipitation flux
including perturbations due to ELF hiss variability.
B - 66
0.001 0.01 0.1 I 10 100 1000 10000
Ion-Electron Pair Production Rate (cm-3 sec-1)
Figure 5. Ion-electron pair production rates in the lower ionosphere
due to radiation belt electron precipitation on September 6, 1966.
The results are given using the pitch angle diffusion coefficients
of Lyons et al . (1972) and the energy deposition program of Walt et
al. (1968). The dependence on the ELF mean amplitude is given for
the range 1 my to 300 my (for details see Spjeldvik and Thorne, 1975a)
in general, the qualitative aspects of the operating physical
mechanisms are fairly well established. We know that with the mag-
netic storm refilling of the radiation belt "slot" region the effec-
tive rates of energetic electron precipitation will be correspond-
ingly enhanced even in the complete absence of ELF whistler mode hiss
intensification. Thus, qualitative estimates (category 1) may read-
ily be made. However, using satellite measurements of the precise
extent to which the electron "slot" is being refilled during the
storm main phase together with the empirical knowledge of the most
probable ELF hiss intensification during the recovery phase from
the quiet time levels to 10-150 my or more (e.g. Parady and Cahill,
1973) it is possible to make at least a sem i -quant i tat ive (category
2) prediction.
B - 67
The magnitude of the electron flux injection into the radiation
belt "slot" region varies from storm to storm. We do not yet know
how this varies with the minimum Dst during the storm; however, it
is reasonable to surmise that these quantities should show co-vari-
ation. For post storm prediction we will therefore rely on radia-
tion belt observations during the storm main phase. If the spectral
shapes of the injected electron fluxes do not change substantially
from storm to storm it is possible to establish a prediction scheme
for the D and E region production profiles by a simple scaling of
the detailed computations presented in Figure 5- Let jnRC be the
observed differential energy electron flux at a pitch angle a
(>aQ. ) and energy E early in the recovery phase at time t ; and let
jQirj be the corresponding quantity established for the September 6,
19bb magnetic storm already studied (Spjeldvik and Thorne, 1975a).
We then have the scaling relation
Q=(5OLD
I'm) (p- ) (3)
\jold/ V W-OLD /
where Q and Q are the predicted and previously (e.g. Figure 5)
computed ionospheric ion-electron pair production rates, and B and
B are the corresponding ELF whistler mode mean wave amplitud
or the plasmaspher ic hiss.
es
As time progresses through the recovery phase the electrons will
decay on time scales given in Figure k and scaled according to Eqn.
(3) for other wave amplitudes. The time evolution of radiation belt
electrons following a magnetic storm will then be similar to the
time evolution exemplified in Figure 2, and the precipitation in-
duced D and E region ionization rates will decay correspondingly.
If j in Eqn. (3) is replaced by j" - exp (- (t-tQ)/T ) where T
is the mean electron precipitation lifetime for the energy of an
electron which deposits its energy primarily at height h (e.g. Po-
tema, 1973), then the time evolution of the ionization rates are
forecastable.
Of course, this simplified precipitation prediction scheme
makes assumptions on:
(a) Intensity of the ELF whistler mode plasmaspher ic hiss.
(b) The spectral shapes of the radiation belt electron injec-
tion flux.
The use of (a) to upgrade the predictability to category 3 re-
quires further research on the hiss generation, particularly its
association with substorms. In principle, there is no difficulty
in using (b) . However, this would require the use of an extensive
computer code (such as the one of Walt et al., 1 968 or Monte Carlo
Methods) on a real time basis for each storm period.
B - 68
6. D REGION IONIZATION CHANGES
The D region ionosphere has been found to contain a number of
different charged particles. Free electrons and light positive
ions (N_+, 0»+ and N0+) are formed by the ionization mechanism.
Heavier ions are formed through the attachment processes, ion-
molecule reactions and formation of hydrated cluster ions.
Realizing that the positive ions appear to fall into two clas-
ses, light ions with small recombination coefficient and heavier
ions with substantially larger recombination coefficient, and that
the negative ions likewise can be divided into the high electron
affinity heavy species and the lower affinity light species, Spjeld-
vik and Thorne (1975b) developed a simplified multi-species ionic
model that has been used to study the storm after effects.
Using this model we have determined the value of the effective
recombination coefficient a rj- defined such that
ef f
d[N] n r i2
-dT" = Q " Vf [e]
00
where [N] is the number density sum of all negative particles, Q is
the ion-electron pair production rate and [e] is the number density
of free electrons. The analytic form of a rf can easily be deduced
from the model of Spjeldvik and Thorne (l9/5b). The a ff height pro-
file for daytime conditions is given in Figure 6. At night the
atomic oxygen concentration below 80 km becomes very small and the
chemistry favors the high affinity negative species. On the other
100
90
£
80
x:
I
70
60
50
40
i i i nun — i i i Mini — i i i mill — i i i mm i i i inn
Middle Latitudes, Day
1 i i i "nil i i I mill I I I llllll L_LLU
10
-7
10
-6
10
,-5
10
•4
10
-3
10
,-2
Effective Recombination Coefficient (cm~3sec ')
Figure 6. Effective recombination coefficient for the daytime lower
ionosphere calculated from the ionic chemistry model of Spjeldvik
and Thorne (1975b).
B - 69
hand, substantially increased ion-electron pair production at night
tends to favor the lighter species. Consequently, the nocturnal
values of a ff are dependent on Q, or for the case of radiation belt
electron precipitation on the trapped flux level of energetic elec-
trons (with a. > an| ) and the scattering ELF hiss amplitude. For
the trapped fluxes of September 6, 1966 we present in Figure 7 the
dependence of a ff on the plasmaspher ic hiss intensity. This depen-
dence is of course strongest below 80 km and above ^ 50 km (below
which the electron precipitation effects are weak).
c
a>
H—
a>
o
o
JO
E
o
o
a>
LxJ
o7
o6 L
n5
aeff Calculated for the
September 6, 1966
Geomagnetic Storm
L = 4, Night
"i — 1 1 1 1 1 11
50 km
75 km
90 km
1 1 1 1 1 n
10 100 1000
Plasmaspheric Hiss Amplitude {my)
Figure 7. Effective recombination coefficient for the nighttime
lower ionosphere calculated from the ionic chem istry model of Spjeld-
vik and Thorne (1975b). The a rr values are found to be dependent on
the ion-electron pair production rate Q and therefore for a given mag
netic storm (Sept. 6, 1 966 in this example) on both the trapped radia
tion belt flux level and the ELF wave intensity B
V
B - 70
It should be noted that the simplified formula {k) really repre-
sents a carryover from earlier considerations of only one kind of
D-region ion. With the recognition of a variety of ions (4) may
still be used provided a rc is considered a variable with atmos-
pheric composition and production rate Q (and consequently with [e] )
For example, Haug and Landmark (1970) have demonstrated restrictive
conditions under which aeff ^[e]"1 near 80 km and similar features
are found by others (e.g. Haug and Thrane, 1970; Folkestad et al.,
1972; Lastovicka, 1975) .
For steady state conditions (d/dt ■* 0) the electron density is
just given by [e] = /Q/a 71 where the appropriate values of Q and
a rr may be obtained from Figures 5, 6, and 7.
This is valid if Q remains unchanged for tens of minutes during the
day and typically 1-2 hours during the night. Thus, in a very sim-
plified fashion it is possible to predict the D region chemical re-
sponse in free electrons by a simple scaling of the detailed calcu-
lations already carried out (e.g. Spjeldvik and Thorne, 1975b).
ACKNOWLEDGEMENTS
One of us (W.N.S.) was supported by a NASA grant W13952.
REFERENCES
Belrose, J. S. and L. Thomas (1968): "Ionization Changes in the Middle
Latitude D-Region Associated with Geomagnetic Storms", Journal of
Atmospheric and Terrestrial Physics, 30, 1397-
Davidson, G. T. and M. Walt (1977): "Loss Cone Distribution of Radiation
Belt Electrons", Journal of Geophysical Research, 82, 48.
Davis, J. R. (1976): "Localized Nighttime D-Region Disturbances and ELF
Propagation", Journal of Atmospheric and Terrestrial Physics, 38 ,
3674.
Folkestad, K. , E. V. Thrane and B. Landmark (1972): "A Study of Ion-
Pair Production Rates and Electron Number Densities in the Ionospheric
D-Region", Journal of Atmospheric and Terrestrial Physics, 34 , 963.
Haug, A. and B. Landmark (1970): A Two-Ion Model of Electron-Ion Recombi-
nation in the D-Region," Journal of Atmospheric and Terrestrial Physics,
32, 405.
Haug, A. and E. V. Thrane (1970): The Diurnal Variation in the Mid-Lati-
tude D-Region" Journal of Atmospheric and Terrestrial Physics, 32,
1641.
Kimura, I. (1966): "Effects of Ions on Whistler-Mode Ray Tracing", Radio
Science, 1 , 269-
B - 71
Krivsky, L . (1977) : "Solar Proton Flares and Their Prediction", Czechoslovak
Academy of Sciences Astronomical Institute Publication #52, Prague.
Larsen, T. R., J. B. Reagan, W. L. Imhof, L. E. Montbriand and J. S.
Bel rose (1976): "A Coordinated Study of Energetic Electron Precip-
itation and D-Region Electron Concentrations over Ottawa During
Disturbed Conditions", Journal of Geophysical Research, 81 , 2200.
Larsen, T. R. , T. A. Potemra, W. L. Imhof and J. B. Reagan (1977):
"Energetic Electron Precipitation and VLF Phase Disturbances at
Middle Latitudes Following the Magnetic Storm of December 16,
1971", Journal of Geophysical Research, 82, 1519-
Lasstovicka, J. (1975): "On the Linearity of the Dependence of the A3
Ionospheric Absorption at 2775 kHz on the Intensity of Ionizing
Radiation", Journal of Atmospheric and Terrestrial Physics, 37 , 1505.
Lauter, E. A. (1977): "A Catalog of Excessive Absorption (Post-Storm
Ionization Enhancements) in the Mid-Latitude D-Region 1948-1976",
Akademie der Wi ssenschaf ten der DDR, HH I -STP-Report 10, Berlin.
Lauter, E. A. and R. Knuth (1967): "Precipitation of High Energy Particles
into the Upper Atmosphere at Medium Latitudes after Magnetic Storms",
Journal of Atmospheric and Terrestrial Physics, 29, 411.
Lauter, E. A., J. Bremer, A. Grafe, I. Deters and K. Evers (1977): "The
Post-Storm Ionization Enhancements in the Mid-Latitude D-Region and
Related Electron Precipitation from the Magnetosphere", Akademie
der Wissenschaften der DDR, HH I -STP-Report 9, Berlin.
Lyons, L. R. , R. M. Thorne and C. F. Kennel (1971): "Electron Pitch
Angle Diffusion Driven by Oblique Whistler-Mode Turbulence",
Journal of Plasma Physics, S_, 589-
Lyons, L. R., R. M. Thorne and C. F. Kennel (1972): "Pitch Angle Diffusion
of Radiation Belt Electrons within the Plasmasphere", Journal of
Geophysical Research, 77 , 3455.
Lyons, L. R. and R. M. Thorne (1973): "Equilibrium Structure of Radiation
Belt Electrons", Journal of Geophysical Research, 78, 2142.
Lyons, L. R., and D. J. Williams (1975): The Storm and Poststorm Evolution
of Energetic (35~560 keV) Radiation Belt Electron Distributions",
Journal of Geophysical Research, 28 , 3985.
Parady, B. K. and L. J. Cahill, Jr. (1973): "ELF Observations during the
December 1971 Storm", Journal of Geophysical Research, 78, 4765.
Parady, B. K. , D. D. Eberlein, J. A. Marvin, W. W. L. Taylor and L. J.
Cahill, Jr. (1975): "Plasmaspher ic Hiss Observations in the Evening
and Afternoon Quadrants", Journal of Geophysical Research, 80, 2183-
B - 72
Potemra, T. A. and A. J. Zmuda (1970): "Precipitating Energetic Electrons
as an Ionization Source in the Midlatitude Nighttime D-Region",
Journal of Geophysical Research, 75 , 7161.
Potemra, T. A. (1973): "Precipitating Energetic Electrons in the Mid-
Latitude Lower Ionosphere", In: Physics and Chemistry of Upper
Atmospheres , Ed.: B. M. McCormac, p. 67.
Russell, C. T., R. E. Holzer and E. J. Smith (1969): "Observations of
ELF Noise in the Magnetosphere: I. Spatial Extent and Frequency of
Occurrence", Journal of Geophysical Reseach, Ik , 755.
Smith, E. J., M. A. Frandsen, B. T. Tsurutani, R. M. Thorne and K. W.
Chan (197*0: "Plasmaspher ic Hiss Intensity Variations During Magnetic
Storms", Journal of Geophysical Research, 79 , 2507.
Spjeldvik, W. N. and Thorne, R. M. (1975a): "The Cause of Storm After
Effects in the Middle Latitude D-Region", Journal of Atmospheric
and Terrestrial Physics, 37 > 777.
Spjeldvik, W. N. and R. M. Thorne (1975b): "A Simplified D-Region Model
and its Application to Magnetic Storm After Effects", Journal of
Atmospheric and Terrestrial Physics 37, 1313.
Spjeldvik, W. N. and R. M. Thorne (1976)): "Maintenance of the Middle
Latitude Nocturnal D-Layer by Energetic Electron Precipitation",
Journal of Pure and Applied Geophysics, 114, 497.
Spjeldvik, W. N. (1977): "Radiation Belt Electrons: Structure of the
Loss Cone", Journal of Geophysical Research, 82 , 709-
Spjeldvik, W. N. (1978): "Reply to the Comment of Walt and Davidson",
Journal of Geophysical Research, 83, 226.
Thorne, R. M. and C. F. Kennel (1967): "Quas i -Trapped VLF Propagation in
the Outer Magnetosphere", Journal of Geophysical Research, 72 , 857-
Thorne, R. M. , E. J. Smith, R. K. Burton and R. E. Holzer (1973):
"Plasmaspher ic Hiss", Journal of Geophysical Research, 78 , 1581.
Thorne, R. M. , and J. N. Barfield (1976): "Further Observational Evidence
Regarding the Origin of Plasmaspher ic Hiss", Geophysical Research
Letters, 3_, 29.
Walt, M., W. M. MacDonald and W. E. Francis (1968): "Penetration of
Auroral Electrons into the Atmosphere", in: Physics of the Magneto-
sphere , Ed: Carovillano, R. C.
Walt, M. and G. T. Davidson (1978): "Comment on 'Radiation Belt Electrons:
Structure of the Loss Cone' by W. N. Spjeldvik", Journal of Geophysical
Research, 83, 225.
B - 73
C. IONOSPHERIC PREDICTIONS
GEOMAGNETIC ACTIVITY CONTROL OF IONOSPHERIC VARIABILITY
Michael Mendi 1 lo
and
Francis X. Lynch
Astronomy Department
Boston University
Boston, MA 02215 USA
John A. Klobuchar
Air Force Geophysics Laboratory
Hanscom AFB
Bedford, MA 01731 USA
1.
INTRODUCTION
Every ionospheric parameter varies in space and time.
Given the sparcity of ionospheric observing stations and the
cost factors associated with creating new ones, one must often
resort to prediction schemes in order to have an estimate for
a particular parameter. Given the fact that an observed para-
meter (P (t)) is not the same every day, one can define a mean
or median diurnal pattern P (t) for each month. The standard
deviations for the observed P (t) may be denoted 0* (t) , and
thus a month's worth of observations at a given site {p (t) }
may be described in the average as P (t) ± a (t) .
o o
The crux of the problem facing ionospheric forecasters
centers on the need to know the diurnal values of P at a site
where observations are not available. The main approach to this
problem has centered on the use of large ionospheric data bases,
£ {P (t)}, which are analyzed in statistical ways to search for
trends and correlations which may aid the long and short term
needs of forecasters. The main goals a. statistical analysis of
ionospheric data can hope to achieve with respect to the form-
ulation of prediction schemes are:
(1) Specification of the magnitudes of the standard devia-
tions for each parameter, and thus the determination
of whether or not predictions of average monthly
behavior (P(t)) can realistically address the needs of
individual users.
(2) A search for statistically significant patterns of
ionospheric variability and thus reduce the uncertain-
ty implied by the ± O values attached to any predict-
ed P ( t ) curve .
(3) An examination of the correlations between ionospheric
variability seen at different sites in order to extend
individual measurements to cover a wider geographical
area.
C - 1
A
areas ,
have be
(1973 )
radio p
ly crit
f Fl an
1§00 LT
pr es sed
ally le
wi thin
found t
being g
re ached
i ty of
can be
that fo
predict
account
has , in
of f E
dieted
e t . al ,
great ma
and thus
en formu
has revi
r opaga ti
ical fre
d f F2 ,
period ,
in perc
ss than
± 12% of
o be onl
reates t
by Rush
f E and
° j 4.
used to
re caster
ing aver
the inh
fact* b
and f Fl
to withi
1971) .
ny studies have
approaches tow
lated for sever
ewed the situat
on conditions a
quencies for th
respectively) .
the observed s
ent with respec
6% -- implying
their median v
y slightly more
during solar ma
was that for m
f Fl is such th
represent the d
s ' attention sh
age behavior, r
erent variabili
een a fruitful
at mid-latitud
n an accuracy o
been carried out in each of these
ard realistic prediction schemes
al ionospheric parameters. Rush
ion for short-term predictions of
t mid-latitudes by examining hour-
e E, Fl and F2 regions (i.e., f. E,
For the E-region during the 0900-
tandard deviations for f E (a ex-
t to a monthly median) were gener-
that 95% of all observations lie
alue. For f Fl , the O (%) were
variable with the difference
ximum years. The conclusion
ost needs the day-to-day variabil-
at monthly median (or mean) values
iurnal variations. This implies
ould be given to the methods of
ather than to ways of taking into
ty of the E and Fl regions. This
avenue in that the median values
e can, for the most part, be pre-
f ± 5% (Muggleton, 1972; DuCharme
For
Rush (19
provide s
in f F2
o
season o
while th
dent par
MHz) , th
of view
ical fre
density
maximum
(NmE , Nm
for thei
the F
76) , f
a goo
behavi
r sola
e expe
ame ter
e phy s
is the
quency
by f (
elecxr
Fl , Nm
r resp
2 region,
or example
d estimate
or at mid-
r cycle co
rimen tally
is often
ically imp
e le ctron
or plasma
MHz) - [9 N
e
on density
F2) are pr
ective cri
the situation is quite the opposite.
, suggests that an average value of ±15%
for the standard deviations observed
latitudes, regardless of local time,
nditions. It should be emphasized that
measured and propagation system depen-
a critical frequency, e.g., f F2 (in
ortant parameter from a modeling point
density (N , in #el/cm3). Since a crit-
frequency, f , is related to electron
(10Gel/cm3 )f* ,Pthe variabilities in the
, G (Nm) , of each ionospheric region
oportionally larger than those quoted
tical frequencies (f E, f Fl , f F2).
o o o
Some ionospher i cally-af f e
on the electron densities them
large standard deviations abou
come the variability factor of
satellite navigation and detec
in accuracy by the time delay
passage through the entire ion
electrons contained along a ve
sphere is called the Total Ele
capable of being measured rout
techniques (Titheridge, 1972)
occurs in the F2 region, the 1
assembled since the mid-1960's
cted propagat
selves and th
t average mon
prime concer
tion radar sy
imposed upon
osphere. The
rtical ray pa
ctron Content
inely by sate
Since 90%
arge TEC data
is a valuabl
ion systems d
us their rela
thly conditio
n. For examp
stems can be
their RF sign
total number
th through th
(TEC) , a par
llite radio b
or more of th
base which h
e source for
epend
tively
ns be-
le,
limi ted
al' s
of
e iono-
ame ter
eacon
e TEC
as been
F2
C - 2
region s
study of
observed
behavior
hemi sphe
by a (%)
J o
dependen
condi tio
gle mid-
mean diu
tionship
coe f f i ci
at least
be direc
behavior
corr e c t
region .
f aci ng E
tudies. Re
TEC day-to
standard d
r e cor de d a
re . They c
, was appro
ces upon lo
ns . Hawki n
la ti tude si
rnal curve
between TE
en t hi ghe r
for mid-la
ted toward
, but rathe
for ) the i n
Thi s , as w
and Fl reg
cently ,
-day va
evi atio
t an 11
onclude
ximatel
cal tim
s and K
te (Sag
for TEC
C and s
than 0.
ti tudes
improve
r towar
he rent
e have
ion pro
Johanson e
riability e
ns , a (%) ,
o
-station ne
d that TEC
y ± 25% wit
e , season,
lobuchar (1
amore Hill/
may be pre
ol ar flux w
9 for all m
, a forecas
d pre di ctio
d the searc
day-to- day
seen , is pr
gnos t i cator
t. al. (1977) described a
ffects by analyzing the
from monthly mean TEC
twork in the northern
variability, as described
h only small additional
latitude and solar flux
974) showed that for a sin-
Hamilton MA) , the monthly
dieted via a simple rela-
hich has a correlation
onths. This suggests that,
ter's attention should not
n schemes for average
h for ways to predict (or
variability of the F-
ecisely the opposite view
s .
2. POSSIBLE APPROACHES TO THE VARIABILITY PROBLEM
As discussed in the previous section, we may assume that a
prediction for the monthly mean diurnal behavior of an F2-region
parameter (Nmax or TEC) is available. We denote this prediction
P(t) and attach to it some error ( ±e ) from the observed mean be-
havior P (t) . Associated with P (t) is an observed standard de-
o o till
viation ±0 ; it is generally agreed that e < \0 by approxi-
O i i i i
mately a factor of _2. Thus, as a first approach to modifying a
monthly prediction P(t) for day-to-day variability effects, it
makes good sense to concentrate on reducing the impact of the
magnitude of a .
of
Cor
of
sea
sul
men
ano
ava
cen
Dep
red
pre
red
an
sou
Rush (1976) considered the case for sho
f F2 via real-time updates from a network
o
relation coefficients for Af F2 were obta
station separation distances for a full r
sonal and north-south vs. east-west condi
ts were used to test the concept of using
ts at one site to update monthly median-b
ther site. Thus, consider th_e case that
ilable while at site B only P(t)±0 exist
tage departures from median conditions at
ending upon the separation between A and
uce the uncertainty at B associated with
diction, that is, a ■*■ O ' . Rush found th
uced by 50%, the approximate separation d
extrapolation/update had to be less than
th sites and 1000 km for east-west sites.
rt-term predictions
of s tations .
ined as a function
ange of local time,
tions. These re-
real-time measure-
ased predictions at
at site A data are
s. Based on per-
A, P ( t)-*-P * ( t) at B
B, this update can
its monthly median
at for O to be
istances for such
500 km for north-
Thus , i t was
concluded that to achieve this degree of improvement under most
conditions at mi d- 1 a ti tudes an observational network would be
required capable of reporting real-time ionospheric measurements
from a global grid 10 in latitude and 20 degrees in longitude.
In a broad sense, this represents "state of the art" conclusions
for the day-to-day variability problem.
An aspect of F-region behavior long associa
variability question is the role geomagnetic act
determining the magnitudes of O at any given si
many studies have been carried out concerning io
and so the crucial points concerning storm effec
more general problem of ionospheric variability
The se i nclude :
(1) The "worst case" departures of an F-re
from average monthly conditions invari
during geomagnetic disturbance.
(2) At most ionospheric sites, storm-time
average conditions exhibit well define
negative phases, which themselves ofte
nounced local time, seasonal and solar
de ncie s .
(3) Ionospheric disturbances associated wi
storms often show long-lived effects i
geomagnetic parameters.
ted with the
ivity plays in
te . A gre at
nospheric storms,
ts vis a vis the
are known.
gion parameter
ably occur
departures from
d positive and
n have pro-
cycle depen-
th geomagnetic
n comparison to
The ionospheric
storm effects. Supe
applied to the probl
tion schemes" for up
able (Mendillo and K
of the storm-time ch
storm period are, al
standard deviations
pattern. This impli
with strong geomagne
using month ly statis
and potentially usef
Consider, for exampl
the days by a suitab
categories ranging f
We denote these 5-da
Results of storm eff
D days) implicitly t
For example :
(1) The standa
be smaller
(2) If the amp
corre c tion
the domina
turbed day
TEC parameter is well-suited for
rimposed-epoch types of analyses h
em and well-defined, quantitative
dating monthly median predictions
lobuchar , " 19 79 ) . The standard dev
aracteristic correction curves for
most without exception, much large
associated with a monthly mean or
es that for days that are not asso
tic activity, the artificial restr
tics may be exploited to yield qua
ul information about day-to-day fo
e, a 30-day month for which we hav
le geomagnetic parameter into six
rom very quiet to very disturbed c
y periods as QQ , Q, q, d, D and DD
ects in the TEC data (essentially
ell us something about the remaini
s tudy ing
ave been
" corre c-
are avail-
iat ions
a 4-day
r than the
me dian
cia ted
i c tion of
nti ta tive
re cas ting .
e ordered
5-day
o ndi tions .
days .
the DD and
ng days .
rd deviations for the QQ to d days must
than the observed a for the entire month.
litudes and phases (+ or -) of storm-time
s are reasonably well-defined, then at least
nt phase of the variations for the non-dis-
s can be inferred.
obta
near
clin
1976
cove
L =
(Ken
des c
geom
F- re
ic f
We have tested these approaches in several ways using TEC
ined from the AFGL latitudinal network of observing sites
the 70 W meridian. The data base available covered the de-
ing and minimum portions of the past solar cycle (-1971-
). Four stations are selected for discussion in order to
r the geomagnetic sites characterized by L = 5 (Narssarssuaq),
4 (Goose Bay) , L = 3 (Sagamore Hill/Hamilton) and L = 2
nedy Space Flight Center) . In the following section, we
ribe results of a preliminary analysis which attempts to use
agnetic activity as a key to specifying the hierarchy of
gion variability contained in statistically-based ionospher-
ore cas t s .
3. RESULTS
The initial search for a geomagne ti cally-con trolle d hier-
archy to F-region variability should concentrate on extreme
cases, and thus our first analysis centered on defining the
essential differences between very quiet days (QQ) and very
disturbed days (DD) . Hourly values of ionospheric TEC data for
each site were used to form percentage variations from monthly
mean conditions for the 5-QQ and DD-days of each month. The
average diurnal behaviors (QQ and DD) , averaged over all months,
are given in Figure 1 (a) Narssarssuaq, (b) Goose Bay, (c)
Hamilton and (d) KSFC . When examined in this way, a remarkable
degree of consistency emerges in that the QQ and DD curves are
virtually "mirror images" for all local times at all four
stations. This dichotomy does not always extend to precise
magnitudes and phases, nor to the zero percentage line as the
"mirror point" -- but nevertheless it does suggest a strong
ordering influence related to geomagnetic activity. Previous
studies have shown that ionospheric storm morphologies are best
ordered by a supe rimposed-epoch scheme carried out for several
days, and thus a single curve labeled "Disturbed Day Variation"
cannot capture the true and often multi-phase development of an
ionospheric storm (Mendillo, 1978). The DD curves presented
here thus point to the most long-lived effects associated with
storms -- and therefore the QQ curves describe the absence of
these perturbations. Consider, for example, daytime effects
over the L = 2-5 range. At high latitudes, the DD curves show
essentially negative effects while enhancements appear at L = 2.
Consequently, the QQ variations also exhibit a 1 ati tudin al ly
dependent phase change. Thus, if one considers "QQ-like
behavior" versus "DD-like behavior" then the spatial extent over
which correlations occur may be greatly enhanced. The implica-
tion to forecasters is obvious, as will be discussed more fully
be low .
NARSSARSSUAQ ( 36 MONTHS )
• — " ■ OQ Days
' ' ■ DD Days
0 2 4 6 8 10 12 14 16 18 20 22 U.T.
20 22 0 2 4 6 8 10 12 14 16 18 L.T.
<
<
o
UJ
<
a:
UJ
50
/ v
/ •
■ / \
/ \
/ \
A >
/ \ f
1 \ /
GOOSE BAY ( 55 MONTHS)
40
30
20
10
• • • QQ Days
•— • — • DD Days
C£Q=±I5% /
0
C^^-^ ^-C /
1 1 1 1 1
-10
20
^ = ±25% \
\
\
\
\
\
•
i i 1_ i 1_ ..j
0
2
4
6
8
10
12
14
20
22
0
2
4
6
8
10
16 18 20 22 U. T,
12 14 16 18 L.T.
Figure 1.
Average diurnal behavior of ATECC%) for the 5 QQ-days
and the 5 DD-days of a month for
(a) Narssarssuaq and (b) Goose Bay.
C - 6
<
a:
<
>
I-
UJ
o
0T
LJ
CL
UJ
O
<
UJ
>
<
25
20
15
10
5
0
-5
-10
-15
-20
SAGAMORE HILL / HAMILTON
(1 15 Months)
•— • — ■ QQ Days
•— ■ — • DD Days
05Q=±I6%
x
o£D=±28%
J L
J_
_L
JL
0 2 4 6 8 10 12 14 16 18 20 22 U.T.
19 21 23 I 3 5 7 9 II 13 15 17 L.T.
DC
0
19
2
21
20
18
#'
.A
KENNEDY SPACE
(34 Months)
FLIGHT
CE
/
NTER
(FDD = ±3I%
16
14
12
10
8
6
4
2
0
-2
• • • QQ Days
\ - — — DD Days
\
\
V
N.
\
\
\ >
\ S
\ T
\ /
• /
\ /
\ /
\ /
Y
J \
/ \
• — • — \
/ \
/
/
/
/
/
r
i
/
\
\
\
\
\
1 1 1
/
/
V'
1 1
-4
-6
■
1
__^
-8
^0 = ± 17 %
1 1 1
1 1
4
23
10
5
14
9
18
13
20
15
22
17
U.T
L.T
Figure 1.
Average diurnal behavior of ATEC(.%) for the 5 QQ-days
and the 5 DD-days of a month for
(c) Hamilton and (d) Cape Kennedy.
25
z
20
o
h-
<
15
or
$
10
h-
2
5
Ul
o
OT
0
Ul
0_
Ul
-5
O
<
or
-10
UJ
^>
<
-lb
-20
SAGAMORE HILL / HAMILTON
(37 Summer months)
■ — ■ — • QQ Days
-- •-- DD Days
05Q=±I5%
X
X
X
X
crDD = ±22%
x
0 2 4 6 8 10 12 14 16 18 20 22 U. T.
19 21 23 I 3 5 7 9 II 13 15 17 L.T.
25
20 V
o
h-
15
<
or
<
10
>
h-
5
Ul
O
0T
0
Ul
n
-h
UJ
e>
<
-10
Ul
§
-15
-20
SAGAMORE HILL / HAMILTON
(40 Winter months)
QQ Days
DD Days
5;D = ±28%
G^Q=±I3%
0
2
4
6
8
10 12 14 16
18
20 22
U.T
19
21
23
1
3
5 7 9 II
Figure 2 .
13
15 17
L.T
Average diurnal behavior of ATEC(%) for the QQ-days and DD-days
for Summer and Winter months at Hamilton (L - 3) .
C - 8
Si
vari a ti
f o 1 lows
Hamilto
very li
10:00 -
Winter
curves
rate de
analy si
seasona
for all
nee 10
ons , i
a sea
n QQ/D
ttle v
16: 00
breakd
are mu
script
s s imp
1 depe
latit
nosphe
t is n
sonal
D curv
ariati
LT pe
own o f
ch lar
ion o f
ly be c
nden t .
ude re
ric storm
ot surpris
control .
es for all
on from mo
riod . Fig
the same
ge r and o f
QQ behavi
ause the s
This is
gions (Men
effects have well-known seasonal
ing that the QQ behavior also
For example, in Figure 1 (c) , the
months averaged together show
nthly mean conditions during the
ure 2 contains a Summer versus
data base; the amplitudes of the
different sign and thus an accu-
or at L = 3 requires a seasonal
torm effects at L = 3 are strongly
not necessarily the case, however,
dillo , 1978) .
The results presented in Figure 1 and 2 suggest that a
knowledge of ambient geomagnetic conditions may be sufficient
to achieve a meaningful real-time update to monthly mean pre-
dictions of F-region behavior. It would appear that several
implementation schemes for this information should be considered
and tested. For illustration purposes, we concentrate here on
the case where geomagnetic information is available to pre-
dict that a day is probably one of the 5 QQ-days of the month.
For the site in question, where P(t)±CF (t) is the predicted
monthly mean pattern and associated variability, one could up-
date this value in several possible ways:
(1) Using curves similar_to those shown in Figures 1 and
2, one could update P(t) by the appropriate AP ( % )
and assign a new uncertainty ±Oqq. This type
of scheme would require interpolation according to
geomagnetic latitudes, with a full breakdown of
seasonal effects in the QQ(t) patterns and their
associated standard deviations CTgg. Thus, each of the
QQ dav_s would have a predicted diurnal pattern changed
from p(t) ± a (t) to P(t) + APgg(t) ± CJgg(t). Since
(7gg(t) is demonstrably smaller in magnitude than a
(usually quoted to be ± 25%) , an updated value with
reduced uncertainty (say to ± 15%, i.e., a 40%
improvement) has been achieved.
(2) An alternate scheme could take advantage of the fact
that Figures 1 and 2 show that during certain local
time periods and seasons, the QQ patterns fall well
to the positive or negative side of the mean behavior.
Thus, knowledge that a certain day is a QQ day implies
that only the positive or negative half of the excur-
sion associated with ± O is likely to occur and up-
o
dates should be made accordingly. Under such condi-
tions^ the monthly mean based prediction
P Ct) ±
u
a a
for positive effects
0* (t) would be changed to:
o
or
P(t) [1
P(t) [1
_°1 ± _°
2 J " 2
a a
- 7°1 ± T°
for negative effects
(1)
(2)
C - 9
TOTAL ELECTRON CONTENT(NT) T
KSFC
I I I I I I I | I I I I I I I | I II I I I I | I I I I I I
00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 24
SD1
LOCRL TIME
SD2 SD3
SD4
AVE
RAGE DISTURBED DAILY VARIATIONS
SD FOR WINTER STORMS
KENNEDY SFG - TEC {VARIATION FROM MflNTHLT HEflN)
30^ WINTER RVERAGES (12 MOS.J LECEND' i " qq
CE
I—
.-z:
LU
(_)
DC
IXJ
20 4—1 — i i i — i i i — i i i — i — i — i — »— h — i — \— i — i — i — i — i — i
0 2 4 6 8 10 12 14 16 18 20 22 UT
h-H — I — I — I — I I < — h- 1 — I — I I I — I — I — I — l-H — I — »-H — I — I
1921 23 1 3 5 7 9 11 13 15 17 LT
Figure 3 .
ta) Average Disturbed Daily Variations of ATEC(%) for
Winter Storms at Cape Kennedy (L - 2).
Cb) Average diurnal behavior of ATECC%) for the QQ-days and
DD-days for Winter months at Cape Kennedy (L - 2).
10
The end result is again a value updated in magnitude, but now
with an uncertainty reduced by 50%. The possibility thus exists
for using simple positive or negative QQ-pattern sectors to
achieve a 50% improvement in forecasting without recourse to a
large network of real-time observing sites. If real-time mea-
surements can be made, the additional possibility exists of us-
ing a single observation in conjunction with QQ patterns (which
may be either positively or negatively correlated over wide
latitude spans) to forecast F-region updates over regions far
in excess of simple in-phase correlation distances.
4. CASE STUDIES
As an example of the concepts discussed in the previous
sections, Figures 3 and 4 describe geomagnetic hierarchy effects
in the day-to-day variability patterns observed at the lower
mid-latitude site Cape Kennedy (KSFC, L = 2) for the winter
season. The average local time disturbance pattern (SD(TEC,%)
for winter storms at KSFC is given in Figure 3a (Mendillo, 1978).
This is a relatively simple pattern of daytime enhancements
with only small nighttime depletions for each day of the storm
pattern. The absence of both positive and negative daytime
phases causes the DD-day pattern for Winter months (Fig. 3b) to
describe this simple pattern with a 5-day average of approxi-
mately ±20% during the daytime hours. While this type of
correction would suffice for days 2 and 3 of a storm period, it
is factors of 2 to 3 too small a correction for the first day of
a storm. This re-emphasizes the fact that SD. (TEC,LT) , i = 1,4
patterns should be used to update storm periods and not DD-
curves .
The character of the QQ curve represents a more realistic
description for day-to-day effects because (1) the standard de-
viations are lower and (2) the 5 QQ-days of a month are not
usually sequential. To test for the consistency of the QQ vs.
DD descriptions implied by Figure 3b, we examined several Winter
month's worth of KSFC total content data. Figure 4 summarizes
the analysis for the Winter months of 1975 (January, February,
November, December) . The days of the month were ordered by Z Kp
and percentage deviations from the monthly mean were computed
for each UT-hour. The vertical scale in Figure 4 shows 5-day
groupings according to £ Kp and the horizontal axis gives UT/LT
steps. To separate the positive excursions from the negative
excursions for easy visual inspection, cross-hatchings were used
for any hour where the deviation was zero or positive (i.e.,
A TEC> 0) . The clear areas of Figure 4 therefore describe
hourly/daily periods where A TEC < 0. Note that the phases of
the A TEC (%) variations in the top portion of Figure 4 are very
C - 11
m
III 1
i tut
■ 11 ISI
I p.
i o§ I I
J
, Ji
iW 1
I lil I
i 1 !■■
—m
CD CNJ LD
/
i-1
h-^
ZD
—1
a
ho
— oo
— ud
— CT
-"CM
~CD
— UD
— CNJ
"~CD
— CsJ
CNJ
CM
CD
CD
H
N
n #
lllilli
I II I 111
rsi lo cr oo c-* c^
o <3
Figure 4.
Examples of geomagnetic ordering of TEC variability for
Winter months at Cape Kennedy for January (top) and
February (bottom), 1975. Shaded areas give
periods where ATEC(%) > 0.
12
similar to those predicted by the QQ-curve in Figure 3b. For
example, during the daytime period (10:00-16:00 LT) when the
F-region generally attains its largest density values (and
therefore uncertainties are most important) , the negative values
persist on virtually all of the QQ-days shown. As pointed out
in the previous section, a simple knowledge of the plus or minus
side of ± a leads to an updated F-region prediction with a
. 0 .
50% reduction in uncertainty.
5. SUMMARY
We have presented a summary of preliminary findings con-
cerning the search for a geomagnetic activity control of iono-
spheric variability. The results are encouraging in that the
division of a month's worth of F-region data into a geomagnetic-
ally ordered hierarchy may lead to a satisfactory forecasting
scheme for day-to-day variability. The five geomagne ti cally
quietest days of the month (QQ-days) were seen to behave in a
consistent way for a season and station where the disturbed days
had a well-defined pattern. The geomagnetic storm associated
disturbed days within a month are themselves best handled by
superimposed epoch derived average storm patterns,
SD[ATEC(%) ,LT] , for each day of a storm period. Thus, if storm
days and QQ days are removed from a monthly distribution, the
remaining 15-20 days may either fall within acceptable variabil-
ity limits or lend themselves to "QQ-like" or "DD-like"
classifications .
C - 13
REFERENCES
DuCharme, E.D., Petrie, L.E. and R. Eyfrig (1971): A method for
predicting the Fl layer critical frequency, Radio S cience ,
6,369. - —
Hawkins, Gerald S. and John A. Klobuchar (1974) : Seasonal and
diurnal variations in the total electron content of the
ionosphere at invariant latitude 54 degrees, AFCRL-TR-0 294 ,
Air Force Geophys . Lab., Hanscom AFB .
Johanson, J.M. , Buonsanto, M.J. and J. A. Klobuchar (1978) : The
variability of ionospheric time delay, Proc. Symp . Effect
of the Ionosphere on Space and Terrestrial Systems, 24-26
January, 1978, J. Goodman, ed., Naval Res. Lab (in press,
1978) .
Mendillo, Michael (1978) : Behavior of the Ionospheric F-Region
During Geomagnetic Storms, AFGL-TR- 78-009 2 (II), Astron.
Contrib. Boston Univ., Ser. Ill, No. 6, March.
Mendillo, Michael and John A. Klobuchar (1979) : A morphology-
based prediction scheme for the coupled latitudinal and
local-time development of F-region storms; Proceedings of
the Symposium on Solar-Terrestrial Predictions, April.
A describing function of the diurnal
Muggleton, L.M. (1972)
variation of Nm CE ) for solar zenith angles from
J. Atmos. Terr. Phys . , 34, 1374.
0 to 90
Rush, Charles M. (1976) : An ionospheric observation network for
use in short-term propagation predictions, Telecom. J., 43 ,
VIII, 544.
Rush, Charles M. and Joseph Gibbs (1973) : Predicting the day-
to-day variability of the mid-latitude ionosphere for
application to HF propagation predictions, AFCRL-TR- 7 3-0 3 35,
Air Force Geophysics Lab., Hanscom AFB.
Titheridge, J.E. (1972) : Determination of ionospheric electron
content from the Faraday rotation of geostationary satel-
lite signals, Planet. Space Sci. , 20, 353.
\k
A MORPHOLOGY-BASED PREDICTION SCHEME FOR THE COUPLED
LATITUDINAL AND LOCAL-TIME DEVELOPMENT OF F-REGION STORMS
Michael Mendillo
Astronomy Department
Boston University
Boston, MA 02215 USA
John A. Klobuchar
Space Physics Division
Air Force Geophysics Laboratory
Hanscom AFB
Bedford, MA 01731 USA
1.
INTRODUCTION
The ionospheric F-region often experiences noticeable
perturbations during geomagnetic storms. The variations en-
countered generally include several periods during which the
storm effects far exceed day-to-day variability, and thus pre-
diction schemes for "ionospheric storms" would be useful to
many F-region supported radio propagation links and trans-
ionospheric satellite navigation systems. To date, only statis-
tical or morphology-based studies of ionospheric storms as seen
at various specific sites have been developed, but little atten-
tion has been given to using these results in any sort of real
or near real-time prediction scheme. Part of the reason for
this lies in the fact that poorly conceived or excessive aver-
aging techniques used in early ionospheric storm studies tended
to make the resultant "average storm pattern" very small in
magnitude and poorly resolved in local time. Any familiarity
with the often drastic effects seen during individual storms
then tended to reinforce the notion that average storm patterns
containing only small-scale detail offer little useable advice
to the radio propagation community.
In this brief report, we summarize an F-region storm anal-
ysis which yields a coupled latitude/local time description of
average storm effects. The results differ from past studies in
that the selection of events studied and averaging techniques
employed allow the characteristic storm patterns to capture the
essential features of individual storms. The average storm
patterns are thus sufficiently defined in amplitude and resolved
in local time to make the overall morphologies a realistic pre-
diction scheme for F-region disturbance effects.
2. ANALYSIS
The full analysis of ionospheric storms used for this study
C - 15
has be
lies e
conten
gra 1 o
there f
spheri
easi ly
cons i d
co lumn
amoun t
wave e
of Far
mos t o
mete r s
within
ionosp
Fur the
of Far
Mendi 1
en des crib
xclus ive ly
t (TEC) .
f the iono
ore contai
c regions
account f
ere d a me a
ar content
of Farada
xper iences
aday rotat
f the rota
above the
an accura
he ri c con t
r details
aday rotat
lo and Klo
ed by Mendillo (1978) . In brief, the study re-
upon the ionospheric parameter total electron
The ionospheric TEC refers to the height inte-
spheric electron density profile, N (h) , and
ns contributions from all of the various iono-
(D,E,F1 and F2) . Since the F-region N values
or more than 90% of the integral, TEC is rightly
sure of the F-region total plasma content. This
is obtained by continuously monitoring the
y rotation (polarization twist) a VHF radiowave
in traversing the ionosphere. Since the amount
ion depends on the geomagnetic field strength,
tion occurs within the first few thousand kilo-
Earth's surface. It is generally agreed that,
cy of 5-10%, the Faraday technique gives the
ent up to a height of approximately 2000 km.
of the interpretation and data reduction methods
ion observations are given by Titheridge (1972) ,
buchar (1974) and Papagiannis et al. (1975) .
The TEC parameter is a quantity well suited for storm
studies. The major reason for this is that the occurrence of a
disturbed ionosphere does not interfere with the continuous
monitoring of the Faraday effect. Thus, while severe distor-
tions of the N (h) profile may occur, while the VHF signal may
suffer amplitude scintillations due to N irregularities or
. . e ,
absorption effects, the measurement is basically unaffected by
these often drastic processes. Conventional ionosonde measure-
ments, on the other hand, can suffer severe degradations during
storm periods, and thus the events of most interest can be lost
to the very effects under study.
All of the TEC data used in the study were taken from the
AFGL-sponsor ed chain of geostationary satellite observing sites
at (1) Nar ssarssuaq , Greenland, (2) Goose Bay, Labrador,
(3) Sagamore Hill/Hamilton, Massachusetts and (4) The Kennedy
Space Flight Center (KSFC), Florida. The 420-km ionospheric
point used to fix the latitudinal coordinates for the TEC
measured from each site refer to geomagnetic L-shell values of
approximately 5, 4, 3 and 2 for Nars sars suaq , Goose Bay,
Hamilton and KSFC, respectively.
The TEC data base available at each site covered the peri-
ods (1) April 1971-De cember 1975 (Nar ss ar ssuaq) , (2) November
1971-April 1975 (Goose Bay), (3) January 1 9 7 1-De cember 1975
(Hamilton) and (4) November 19 7 3-Sep tembe r 1976 (KSFC). The
geomagnetic storm selection criterion was Ap > 30 for at least
one day of the storm period or Kp(max) > 5. The method for
determining average storm patterns in percent on a local time
basis (SD. (TEC,LT) ,i = l,4) has been described in previous studies
(Mendillo, 1971; Mendillo and Klobuchar , 1974). For the present
case, the monthly median diurnal pattern was used as the control
C - 16
curve, and the storm-associated perturbations were followed over
a 4-day period using hourly resolution in local time. The
relatively large data base yielded a total number of solar-
minimum-epoch storms of 70, 67, 109 and 70 for the L=5, 4, 3 and
2 sites. In addition to computing the average storm patterns at
each site for the entire data set, a subdivision by season was
also used: Summer (May, June, July, August) , Winter (November,
December, January, February) , Spring (March, April) and Fall
(September, October).
Once the average storm pattern for a given period is ob-
tained at each site, the results are combined by constructing
iso-level contour maps of the percentage deviations on a grid
of invariant latitude versus local time. A contour-plot
representation for TEC quiet and storm-time variations seen
0
along the 70 W meridian chain was described by Mendillo and
Klobuchar (1975). Its generalization to percentage variations
is straight forward, and the procedure offers a compact way of
presenting simultaneous storm patterns obtained over a wide
latitude range.
3.
RESULTS
Figures 1 through
patterns obtained for
according to Summer, F
results for all storms
istic features" seen a
a composite representa
countered over the L -
following points may b
(1) On the day of the
pattern shows that the
and peaks at a later 1
low latitudes in the L
the positive phase has
not seen at the L > 2
(2) Auroral-oval assoc
during the post midnig
values occur equatorwa
prior to 18:00 LT at L
night. This trough-as
gradients maximizes du
pattern repeats on sub
storm effects dominate
range long after the d
5 present the u
all storms, with
all, Winter and
taken together
t the individual
tion of the esse
2-5 latitude
e noted :
storm commenceme
daytime positiv
ocal time as one
=2-5 domain .
both a noontime
s i te s .
iated TEC enhanc
ht hours on Days
rd of the aurora
- 5 and reachin
sociated disrupt
ring the 00-06:0
sequent nights,
the nighttime i
aytime perturbat
nified storm morphology
a seasonal break-down
Spring. In Figure 1, the
show how the "character-
sites may be unified into
ntial storm features en-
range. In particular, the
nt (SC) , the SD (TEC,LT)
e phase grows in magnitude
progresses from high to
At low latitudes (L - 2),
and post-sunset component
ements maximize near L = 4
1 and 2. Depressed TEC
1 enhancements, beginning
g midlatitudes after mid-
ion of the normal latitude
0 LT period on Day 3. The
showing that persistent
onosphere in the L = 3 - 5
ions have subsided.
Figures 2 through 5 contain storm morphology patterns ac-
cording to season. One can see that all of the characteristic
17
65 --
60 --
55
50 --
45--
40 --
TOTAL ELECTRON CONTENT AVERAGE DAILY VARIATIONS OURING MAGNETIC STORMS
50 70 50 3010 K) M 10 40
50 60 40 5 -5
-10 -5 5
06 12 18
DAY 1--SDKTEC)
LMT
DAY 2--SD2(TEC0
A
65
60" -5
55 --
50" -=2'
45--
40"
TOTAL ELECTRON CONTENT AVERAGE OAILY VARIATIONS DURING MAGNETIC STORMS
10 5
5-5 5 5 10 5
5
4
f 3
-- 2
24 LMT
00 06 12 18 24 06 12 18
DAY 3--SD3(TEC) DAY 4--SD4(TEC)
Figure 1.
Average storm patterns for al 1 storms . Contours give ATEC(%)
as a function of invariant latitude (A) and local time (LT) .
C - 18
65 --
60 --
55 --
50 —
45--
40 --
TOTPL ELECTRON CONTENT PVERPGE DAILY VARIATIONS — SUMMER STORMS ---
50 50 30 10 10 10 5 5 10 20 20 5-5-K) -10 -10 -10-5
5
4
3
- 2
5 10 10 20
4060 50 30 10 5
_l 1-
00 06 12 18
DRY 1 — SDK TEC)
24 06 12 18
DAY 2- SD2(TEC)
24 LMT
65 --
60 --
55
50 --
45
40--
TOTRL ELECTRON CONTENT flVERHGE DfilLY VflRIflTIONS
-5 -5 -5 -5 -5
• SUMMER STORMS —
+ 5 +5
-5
5
4
3
-- 2
00
06 12 18
DAY 3--SD3(TEC)
06 12 18
DRY 4--SD4(TEC)
24 LMT
Figure 2.
Average storm patterns for Summer storms . Contours give ATEC(%)
as a function of invariant latitude (A) and local time (LT).
C - 19
A
TOTAL ELECTRON CONTENT AVERAGE DAILY VARIATIONS --- FALL STORMS
70 100 20 20 20
06 12
DRY 1--SDKTEC)
06 12
DRY 2--SD2(TEC)
LMT
TOTAL ELECTRON CONTENT AVERAGE DAILY VARIATIONS --- FALL STORMS
5 -20 -5
65--
60 --
55'--
50'--
45--
40*-
-- 5
-- 4
-- 3
-- 2
00 06 12 18
DRY 3--SD3(TEC)
06 12 18
DRY 4--SD4(TEC)
24 LMT
Figure 3.
Average storm patterns for Fall storms . Contours give ATEC(%)
as a function of invariant latitude (A) and local time (LT) .
C - 20
TOTAL ELECTRON CONTENT AVERAGE DAILY VARIATIONS --- WINTER STORMS --
120 90 100 100
5 10 20 40 40
5 10 30
5
4
3
-- 2
00
06 12 18
DAY I— SDUTEC)
06 12 18
DAY 2--SD2(TEC)
LMT
TOTAL ELECTRON CONTENT AVERAGE DAILY VARIATIONS --- WINTER STORMS
5-10. -5 10 20 20 20 10 5
-5\
00 06 12
DRY 3--SD3(TEC
18 24 06 12
DRY 4--SD4(TEC
-- 2
24 LMT
Figure 4.
Average storm patterns for Winter storms. Contours give ATE C ( % )
as a function of invariant latitude (A. ) and local time (LT).
C - 21
A
65--
60 --
55"
50 --.
45--
40--
TOTflL ELECTRON CONTENT AVERAGE DAILY VARIATIONS --- SPRING STORMS
30 50 30 20
20 20 5 5 20 20
510 20
-- 3
-- 2
12 18
DAY 1--SD1 ( TEC )
06 12
DAY 2--SD2(TEC)
LMT
00 06 12 18
DRY 3--SD3(TEC)
24
-- 3
06 12
DRY 4--SD4(TEC)
-- 2
LMT
Figure 5 .
Average storm patterns for Spring s torms . Contours give ATEC(%)
as a function of invariant latitude (A) and loczal time (LT) .
C - 22
features summarized in Figure 1 occur in each season, and that
clear modulations of those patterns are present. These include:
I. VARIATIONS IN THE AFTERNOON ENHANCEMENTS
(1) The positive phase enhancements on Day 1 maximize at a later
local time in Summer (Fig. 2) than in Winter (Fig. 4) , over the
entire L = 2 - 5 latitude range. During Spring and Fall storms
(Fig. 3 and 5) , the latitudinal progression of the local time of
the afternoon enhancement does not extend below L = 3.
(2) The magnitude of the afternoon enhancement is relatively
insensitive to season at L = 4 - 5, it varies in step with the
so-called seasonal anomaly near L = 3 (i.e., maximum in Winter,
minimum in Summer) , while at L = 2, the seasonal trend is one
of peak enhancements during Summer and Fall, minimum enhance-
ments during Winter and Spring.
(3) At L - 2, where twin maxima occur on Day 1, the initial en-
hancement is strongly confined to the 12-15:00 LT period. Only
during Spring storms does it exceed the magnitude of the late
afternoon enhancement.
II. VARIATIONS IN THE NEGATIVE PHASE
(1) For L > 3, a daytime negative phase occurs during all sea-
sons except Winter; it extends to L - 2 during Summer and Fall.
(2) The intrusion of auroral oval and trough effects to lower
latitudes occurs during all seasons. The nighttime F-region
enhancements at L > 3 associated with particle precipitations
are largest during the SD 1 and SD 2 periods, with lingering
effects still seen on Day 4. The depleti-on effects seen at
L < 3 are due to trough migrations upsetting the normal latitude
gradients. The maximum effect occurs during 00-03:00 LT period
on Day 3 for all seasons, with the strongest depletions extend-
ing to L < 2 during both equinox periods. The persistence of
nighttime effects again occurs for all seasons.
4.
ASSESSMENT OF THE AVERAGE STORM PATTERN CONCEPT
Any casual obs
literally, no two s
one of the main rea
Sagamore Hill storm
the goal of display
which occur at a si
activity. The ques
usefulness (and mea
to this dilemm
I . From the p
esses mos t res
centrate on a
events differ
the mechanism
la may
ioin t
iponsi
s ingl
so f r
whi ch
relatively naive co
erver of ionosphe
torms exhibit ide
sons for publishi
effects (Mendill
ing the great var
ngle site due to
tion naturally ar
ning) of average
be approached al
of view of unders
ble for storms, i
e event, given th
om one another.
causes storm eff
ncept. The fact
ric storms knows
ntical behavior,
ng the AFCRL ATLA
o and Klobuchar,
iety of F-region
increases in geom
ises , then , of th
storm patterns,
ong two avenues:
tanding the physi
t would be foolis
e realization tha
The notion of spe
ects is now known
that perturbation
that, quite
Indeed ,
S of
1974) was
responses
agne ti c
e real
The answer
cal proc-
h to con-
t single
ci f ying
to be a
s exhibit
23
positive and nega
according to seas
nisms operates, w
from event to eve
behavior of a set
nizable pattern--
then the average
truly characteris
will identify the
tude range and th
ed to those capab
ual storms will e
nounced than they
set the limiting
mechanisms .
II . From the poi
phology models, t
patterns. To bas
clearly unjustifi
patterns, constru
down, offer the o
how a model predi
modified to inclu
individual events
case" conditions
tive phases, with considerable variations
on and latitude, shows that a blend of mecha-
i th perhaps a dominance of one over the others
nt and site to site. If, however, the average
of storm events exhibits a clear and recog-
and one reminiscent of many individual events —
pattern must point to features and processes
tic of that site. Thus, the average pattern
features most common at a given site or lati-
e search for operative processes will be limit-
le of causing such effects. Clearly, individ-
xhibit characteristic features much more pro-
appear in the average, and these therefore
tests for the identification of correct
nt of view of wishing to update F-region mor-
here is little choice from using average storm
e predictions upon individual events would be
able, for the reasons mentioned above. Average
cted on a local time basis with seasonal break-
nly reasonable way of providing an estimate of
cting the median or average behavior should be
de disturbance effects. The correct role of
is, once again, to set the limit of "worst-
for a given parameter and/or site.
Finally, it would be good
of the percentage variations p
Perhaps the most frustrating a
the realization that, once the
acteristic storm patterns is a
the patterns are often small a
tions of those values are inva
tion values themselves. We su
for example, by variation valu
not necessarily vague or meani
that the standard deviations o
mean diurnal pattern are gener
value is obtained which is lar
--even if its standard deviati
associated feature has been id
ATEC of say +35% ±45% surely p
stantial TEC enhancemen t--a po
ionospherical ly-suppor te d prop
small average value with a lar
-5% ±30% quoted above) provide
monthly mean pattern cannot be
variability of -25% should now
to comment on the abso lute values
resented in the previous figures,
spect of storm investigations is
goal of obtaining clear and char-
chieved, the absolute values of
nd, moreover, the standard devia-
riably greater than the perturba-
ggest that results characterized,
es of +35% ±45% or -5% ±30% are
ngless numbers. One must realize
f a typical mid-latitude monthly
ally near ±25%. Thus, if an SD(%)
ger than this "normal variability"
on is large — a significant storm-
entified. As in the above case, a
oints to the likelihood of a sub-
tentially valuable update to an
agation system. Similarly, a
ge uncertainty (such as the ATEC =
s the information that while a
significantly updated, the normal
be taken with caution.
Both examples treated above referred to the interpretation
of a single storm-associated SD(%) value. A third case exists,
namely a s tring (from several hours to a few days) of consis-
2k
tently positive or negative SD values of small absolute value
(say < I 10% | ) . This typically happens, for example, during the
negative phase of mid-latitude storm effects when daytime SD
values might be characterized by -5 to -10% for two to three
days. Such consistencies point to the reality of the negative
phase and its longevity. Yet, in striving to theoretically mod-
el neutral atmospheric effects upon F-region loss processes, one
would clearly not aim to produce only a -5% effect.
The
best evidence we
utility of Average Storm
Sagamore
Hill/Hamilton st
Earth have received more
70 W during periods of g
features ,
, first seen in 1
quent solar maximum and m
patterns
for 1968-1969 (M
Klobuchar , 1974) , and now
point to
a consistency be
effects .
And finally, th
storm patterns were never
tification of the "SKYLAB
"hole" which occurred dur
(Mendillo et al. , 1975).
have for
Patterns
udies of
s crutiny
eomagne ti
965 storm
inimum ye
endillo ,
1971-197
tween ave
e reality
more obv
effect"
ing a sev
believing in th
is once again a
the past decade,
than this L - 3
c activity. Cha
data, followed
ars, repeated in
1971) , 1968-1972
5 (Mendillo, 197
rage and individ
and utility of
ious than in the
of the large-sea
ere geomagnetic
e meaning and
return to the
Few sites on
location near
racteris ti c
during subse-
aver age
(Mendillo and
8) , always
ual storm
our average
correct iden-
le F-region
s torm
Acknowledgements
This work was supported in part by contracts F196 2 8- 7 5-C-O 04 4
and F19628- 7 7-R-0310 from the Air Force Geophysics Laboratory
to Boston University. We thank Mr. Michael Buonsanto and
Mr. Francis Lynch for their assistance in many of the technical
aspects of this study.
25
Re f er en ces
Mendillo, Michael, Ionospheric Total Electron Content Behavior
During Geomagnetic Storms, Nature , 234, 23, 1971.
Mendillo, Michael (1978) Behavior of the Ionospheric F-Region
During Geomagnetic Storms, AFGL Tech. Report.
AFGL-TR-78-0092 (II ) , Astron. Contrib. Bos. Univ., Ser. Ill,
No. 6, March, 1978.
Mendillo, M., Hawkins, G.S. and Klobuchar, J. A., A sudden
vanishing of the ionospheric F-region due to the launch
of Skylab, J. Geophys . Res . , 80, 2217, 1975.
Mendillo, M. and J. A. Klobuchar, An Atlas of the Midlatitude
F-Region Response to Geomagnetic Storms, AFCRL Tech.
Report No. 0065, Hanscom AFB , Bedford, Ma. 01731, USA,
1974.
Mendillo, M. and J. A. Klobuchar, Investigations of the Iono-
spheric F-Region Using Multi-Station Total Electron
Content Observations, J. Geophys . Res . , 80, 643, 1975.
Papagiannis, M.D., Ha j eb-Hos seini ch , H. and M. Men_dillo, Changes
in the ionospheric profile and the Faraday M factor with
K
Planet. Space Sci., 23, 107, 1975.
Titheridge, J.E., Determination of ionospheric electron content
from the Faraday rotation of geostationary satellite
signals, Planet. Space Sci., 20, 353, 1972.
26
ON THE POSSIBILITY TO PREDICT VARIATIONS IN THE F2-REGI0N
PARAMETERS AS A FUNCTION OF THE IMF DIRECTION
R. A. Zevakina, E.V.Lavrova
Institute of Terrestrial Magnetism,
Ionosphere and Radio Wave Propagation
of the USSR Academy of Sciences
Moscow, USSR
Variations in the F2-region parameters depending
on the direction of the vertical and radial compo-
nents of the IMF are examined. It is shown that using
data on the IMF direction or those on geomagnetic va-
riations in subpolar regions one can predict the sign
of deviation of fQF2 from the medians.
In the existing short-term predictions of the ionospheric
state (Zevakina, 1975) the changes of the ionosphere due to
anomalous radiation from active solar regions are estimated.
In the present paper, we consider the possibility of predic-
ting the sign of 8 fQF2 variations under magnetically quiet
conditions (+20%). The cause of these variations has not yet
been established. It is supposed that they are due to the vari-
ability of the various processes in the ionosphere. In recent
years, their relation to the solar wind parameters has begun
to be investigated (Kolomiitsev, 1975; Potapova, 1974; Zevaki-
na, 1974; Berezin, 1974; Lyatskaya, 1974). Potapova (1974) and
Zevakina (1974) deal with the variations in f F2 and 1^^ at
the different directions of the radial component of the inter-
planetary magnetic field (IMF). It has been shown that on days
with off-Sun (+) IMF direction the fluctuations of f F2 at
o
high and middle latitudes are in most cases higher than the me-
dian values, whereas on the days characterized by the sunward
(-) IMF direction it is lower. The variability of f F2 has
C - 27
been found to increase when the Earth intersects the sectorial
IMF boundaries (Zevakina, 1974).
Bearing in mind that the magnetic variations are the most
significant in the presence of the southward IMF component
(Ivanov, 1972), we have considered here, apart from the effect
of the radial IMF component, the influence upon the F2-region
variations of the IMF component vertical relative to the eclip-
tic. With this purpose, we have studied the mean 8 f F2 and
Ahp F2 variations separately for the days with the southward
(S) and northward (N) IMF components and for the off-Sun and
sunward IMF directions and also the 8fQF2, Ah F2 and Ah F
variations in intersecting the sectorial IMF boundaries and in
the period of the change of the northward component for the
southward one.
The present study has been carried out using the data of
the ionospheric stations Druzhnaya, Resolute Bay, Murmansk,
Yakutsk, Moscow, Khabarovsk, Alma-Ata, Yamagawa, Delhi, Lwiro,
Raro tonga, Canberra, Hobart, Mawson, and Scott Base obtained
during the years of low (1964, 1972 and 1973) and high (1958,
1967 and 1968) solar activity. The data on the IMF have been
taken from (Wilcox, 1965; Solar T.A. Chart, 1967; Mansurov,
1975) » SfQF2, Ah F2 and Ah' F being determined from the me-
dians on quiet days.
Fig. 1 illustrates the diurnal variations of 8 f F2 at
different latitudes during 1964 and 1958, depending on the di-
rection of the radial IMF component. From this figure it fol-
lows that for the sunward direction of the IMF component, the
8 fQF2 in the northern hemisphere were predominantly negative,
whereas in the southern hemisphere, positive. For the off-Sun
direction of the IMF component, the reverse picture was obser-
ved. When the IMF was directed away from the Sun, however, the
opposite-in-phase of F2 variations in the two hemispheres
are less pronounced than in the case of the sunward direction
and are not always present. Thus, in 1958, when the IMF direc-
tion was off-Sun, the 8f F2 in the northern and southern
c - 28
turn
Iflh
f~~
I I I
?
J l l
00 12 00 12
Pig, 1, Mean diurnal variations
of 8 foF2 for the sunward (-)
and off -Sun (+) IMF directions
at the stations:
a) Resolute Bay, winter;
b) Murmansk, equinox;
c,d) Moscow, equinox and summer
respectively;
e) Khabarovsk, winter;
f) Canberra, winter;
g) Scott Base, winter.
00 12 00 12 LT
hemispheres were positive. But at Resolute Bay they were consi-
derably higher than at Scott Base. The limits of t>fQF2 vari-
ations in 1958 were greater (+ 20%) than in 1964- (+ 10%).
The influence of the IMF upon fQF2 is more pronounced in
winter and on equinoxes, at the near-noon time. The effect is
the most significant within the polar caps, in the region of
the dayside cusp.
We have compared the diurnal variations of Sf F2 during
1967 and 1968 at various radial directions of the IMF with
those of Sf F2 on days with the southward and northward IMF
components. As an illustration, fig. 2 shows such diurnal va-
riations in the equinox periods of 1967 for the stations Reso-
lute Bay, Murmansk, Moscow, and Huancayo.
From this figure and similar ones it follows that for the
sunward IMF direction the Sf F2 variations are similar to
those of 8f F2 on the days of the southward IMF component
and, for the off -Sun IMF direction, it varies in the same man-
ner as on the days with the northward component. In Moscow,
OfQF2 was, on average, negative on days with the southward
29
M 24 0 il 24 0
j_ i i — i — i — i — i
11 24 0 12 24 LT
IMF component and for the
sunward direction, and po-
sitive on days with the
northward compenent and for
the off-Sun IMF direction.
At high and equatorial la-
titudes, the sign of S f QF2
in 1967 and 1968 did not
change with the change in
IMF direction, but for the
southward and sunward direc-
tion, 8f F2 was lower
than for the northward and
off-Sun direction. At equa-
torial latitudes the effect
of IMF is small, though no-
ticeable; it manifests it-
self in that, on days with
the southward component and
the sunward direction of the IMF, 8f F2 is on average some-
what higher than on days with the northward component and the
off -Sun IMF direction.
The variations in the altitude of the F2-region at diffe-
rent IMF directions have been examined using the data of Mos-
cow. With this purpose, Ah F2 characterising variations in
ii have been determined. Table 1 presents Ah F2 during 1968
over the seasons at different IMF directions at night (21 -
02 hrs LT) and in daytime (10 - 15 hrs LT) hours.
From the table it follows that in winter and on equinoxes
Ah F2 is 2 to 3*5 times higher on days with the southward IMF
component than on days with the northward component. In summer
at night Ah is not much higher at the southward component
than at the northward one, whereas in the daytime it is higher
by a factor of 3» though Ah^ themselves are small. On days
with the sunward IMF direction, both in winter and spring, Ah
Fig. 2. Mean diurnal variations
of 8 foF2 in the equinox pe-
riod of 1967 for the different
directions of the radial verti-
cal IMF components at the sta-
tions:
a} Resolute Bay; b) Murmansk;
c) Moscow; d) Huancayo.
30
is 1.4 times higher at night, and 2 to 3*5 times higher in the
daytime than on days with the off -Sun IMF direction. During
summer nights the values of <^k are not significantly diffe-
rent for the sunward and off -Sun directions, but in the day-
time, A hi is three times as high as Ah*. Therefore, the alti-
tude of the F region, just as fQF2 , undergoes the most signi-
ficant change with the change in the direction of the vertical
IMF component.
Table
1
Season
z^h
p
F2
! A.
a+ !
1 AS
<ah
Night
Day
: Night
Day :
:Nigh1
[ +
-
N
s :
+
-
N
s :
: Day
Winter
22
32
19
43
2
7
3
ii
1.4
3.5
2.2
3.6
Spring
23
33
11
49
7
18
7
23
1.4
2.5
4.4
3.2
Autumn
36
24
24
51
3
5
5
16
0.6
1.6
2.1
3.3
Summer
14
15
12
16
7
22
9
24
1.0
3.1
1.3
2.6
In what follows, the variations of the F2 region at diffe-
rent latitudes, which occur when the Earth passes through the
sectorial boundaries of the IMF, are examined. Using the me-
thod of epoch superposition, we have determined the of F2
and Ah F variations during near-noon (11-13 hrs LT) and near-
midnight (21-23 hrs LT) hours for five days before and after
the Earth passes through the sectorial boundaries, for 1958 and
1964. The variations in the average SfQF2 and Ah F during
the daytime and nighttime hours occurring when the Earth pas-
ses through the boundary separating the sector with the off-Sun
field direction and that with the sunward direction during 1964
are presented in fig. 3. The first day of the new sector is ta-
ken as zero.
From fig. 3 it follows that at high and middle latitudes
Of F2 is higher, when the Earth passes through the end of the
31
to,*
a:
8
C 0
-8 -
0
^-fr*
d Sfv^
8p
0
■M
8 -
1 • ~^& -H^-5
4 »— V
w
\jtf
• 1
Mi
Jtf
- -4
4 4
days
0 4
Fig, 5» Mean variations in
Sf0F2 (1) and Ah'P (2) du-
ring five days before and
after the intersection by
the Earth of the IMF secto-
rial boundaries at the sta-
tions: a) Resolute Bay;
b) Murmansk; c) Moscow;
d) Khabarovsk; e) Yamagawa;
f) Lwiro; g) Rarotonga;
h) Canberra; i) Hobart;
k) Mawson; 1) Scott Base,
positive sector, than it is in
the beginning of the negative
sectors during the daytime and
nighttime hours. At low latitu-
des (Khabarovsk, Yamagawa, Lwiro,
and Rarotonga) Sf F2 is lower,
in the daytime for two days be-
fore and after the intersection
of the sector boundaries, than
during the nearest days, while
at night it is higher in the be-
ginning of the sector than at
the end. Thus, the 8fQF2 varia-
tions in the daytime and at
night in the positive sector oc-
curred in phase within the polar
cap and at low latitudes, while
in the negative sector, in the
opposite phase.
It should be noted that
when the Earth goes over from
the negative sector to the posi-
tive no reverse picture is obser-
ved, but the same one. This effect
appears to be due to a change in
not only the sign of IMF on the
sectorial boundary, but also
other solar-wind parameters, be-
cause it is known (Wilcox, 1965;
1968) that the solar wind speed
and the value of IMF are higher
in the beginning of the sector
than at its end, whereas the num-
ber of solar protons is larger at the end of the sector than
at its beginning (Nishida, 1966),
C - 32
n
The variations in latitudes of the F region that occur
at the intersection of sectorial boundaries are on average op-
posite to frequency variations, i.e. in the periods of increase
in Sf F2, the altitudes in most cases decreased by 5 to 10 km,
whereas in the periods of decreasing 8 f F2 they increase by
10 to 20 km (the dashed curve in fig. 3)»
For 1967 and 1968, we have examined, aside from the vari-
ations in the F-region occurring when the sign of the radial
component changes, the 8f F2 variation in periods when the
northward IMF component changes for the southward one. It has
been shown that the change in the sign of the vertical IMF com-
ponent leads to the same S fQF2 variations as the change in
the sign of the radial IMF component. When the northward IMF
component changes for the southward one during the daytime,
there occurs a decrease of SfQF2 at high and middle latitu-
des and an increase of 0 f F2 at equatorial latitudes. At
night 8 f F2 at middle latitudes changes, with the changing
sign of IMF, in the same manner as in the daytime, while within
the polar cap the values of Sf F2 increase in the period of
changing sign and on the subsequent day. The 8 f F2 variations
in the daytime and at night are the most considerable during
the day on which the sign of IMF changes and during two or
three days after the change.
From what we have stated above it follows that the varia-
bility of the F-region at all latitudes is significantly depen-
dent on the direction of the interplanetary magnetic field. The
magnitude and sign of 8 fQF2 and Ah F2 under quiet condi-
tions are determined, to a considerable degree, by the IMF di-
rection. The change in the sign of the vertical component of
IMF brings about more significant variations in the F-region
than the change in the sign of the radial component. However,
the character of 8 f F2 and Ah F2 variations in the case of
the southward component is analogous to that of variations in
the case of the sunward IMF direction, while variations for
the northward component are similar to those for the off-Sun
C - 33
IMP direction.
The change in the sign of the radial and vertical IMP
components produces in the P2 region effects similar to distur-
bances but of lower intensity. The effects due to the IMP are
different from those due to disturbances also in that they are
maximum within the polar cap, at latitudes of the dayside cusp,
whereas the disturbance effects are maximum within the auroral
zone.
The possibility to use the obtained results for predicti-
ons has been tested utilizing the data of five stations, used
in short-term predictions (Zevakina, 1967) as the reference
ones. Prom the data on 0 fQF2 obtained at the stations Druzh-
naya, Murmansk, Yakutsk, Moscow and Alma-Ata we have determined
the diurnal variations of ST^P2 during 1972-1973 over the
seasons for days with the sunward and off-Sun directions.
The 0 f P2 used in ionospheric forecasting services are dif-
ferent from those considered above in that they are determined
using not the median for quiet days, but the sliding ten-day
medians (Zevakina, 1967). Therefore, it was necessary to find
out whether the IMP effect would be pronounced for such data.
The direction of the radial IMP component over the indicated
period has been determined using geomagnetic data (Mansurov,
1973).
Table 2 presents the probabilities for the positive and
negative 0 f P2 at the different IMP directions.
Prom the table it follows that the IMP effect is clearly
pronounced in the periods of equinox, but in winter and summer
it is not so evident.
So, the use of the real time data on the IMP direction is
important for the prediction of the O fnF2 sign especially
in the periods of equinox.
The data presented above suggest that the variability of
the P-region under both quiet and disturbed conditions may be
connected with the variability of the solar wind parameters.
3k
Station
Table 2
Probability of appearance of 8 f F2 < 0 and>0,%
Equinox
Summer
>0 <0 >0 <:0 >0 <0 >0 <0
Winter
>0 <C0 >0 <:0
Druzhnaya
Murmansk
Yakutsk
Moscow
Alma-Ata
90 10 25 75 4-0 60 35 65 -
78 22 22 78 40 60 42 58 55 45 51 69
85 15' 50 70 38 62 47 53 57 43 60 40
90 10 28 72 48 52 40 60 60 40 42 58
78 22 43 57 ^>7 43 38 62 55 45 50 50
The ionospheric effects, just as the geomagnetic ones, appear
to be due to the rearrangement of convection and electric cur-
rents in the magnetosphere (Sorgensen, 1978; Bassolo, 1972)
and ionosphere during the change in the IMP direction (Dungey,
1961).
REFERENCES
Bassolo, V.S., S.M.Mansurov and V.P.Shabansky (1972): In: Inve-
stigations on geomai^netism,aeronomy and solar physics,
issue 23. Irkutsk. 125*
Berezin, Yu.M. , N.P.Ben'kova and G.V.Bukin (1974): Abstracts
to the reports for the All-Union Conference on the Physics
of Ionosphere held in Rostov-on-Don, Moscow, IZMIRAN,96.
Bobrov, M.S. (1973): Astronomicheskii Vestnik. 13, 177.
Dungey, J.W. (1961): Phys. Rev. Letts., Vol. 6, 47.
C - 35
Ivanov, K.G. and N.I.Mikerina (1972): Geomagnetism and aeronomy.
Moscow, USSR Academy of Sciences, 12, 688.
Kolomiitsev, O.P. , S.M.Mansurov and L.G.Mansurova (1975) s In:
Physics and simulation of ionosphere, Moscow, USSR, Nauka,
179.
Lyatskaya, A.M. and V.B.Lyatskii (1974) : Abstracts to the re-
ports for the All-Union Conference on the Physics of Iono-
sphere Held in Rostov-on-Don, Moscow, IZMIRAN, 99.
Mansurov, S.M. and L.G.Mansurova (1973) s Geomagnetism and Aero-
nomy, Moscow, USSR Academy of Sciences, 13, 794- •
Nishida, A. (1966): Rept. Ionosphere and Space Res. Japan. 20,
36.
Potapova, N.I. and B.S.Shapiro (1974) * Geomagnetism and aer ono-
nis, Moscow, USSR Academy of Sciences, 14, 1101.
Solar Terrestrial Activity Chart for 1967, 1968. Science Coun-
cil of Japan, 1973, 1974.
Sorgensen, F.S., E.Friis-Christennsen and J.Wilhjem (1972):
J. Geophys. Res.. Vol. 77, 1976.
Wilcox, J.M. and N.F.Ness (1965): J. Geophys. Res.. Vol. 70,
5793.
Wilcox, J.M. (1968): Space Sci. Rev. . Vol. 8, 258.
Zevakina, R.A., E.V.Lavrova and L.N.Lyahova (1967): Principles
of predicting the ionospheric-magnetic disturbances and
the short-term radioforcast service, Moscow, USSR, Nauka.
Zevakina, R.A. (1974): Abstracts to the reports for the All-
Union Conference on the Physics of Ionosphere Held in Ros-
tov-on-Don. Moscow, USSR, IZMIRAN, 93.
Zevakina, R.A., V.P.Kuleshova, E.V.Lavrova, and L.N.Lyakhova
(1975): Methods of short-term predictions of magnetic ac-
tivity and the state of the ionosphere. (Instruction),
Moscow, USSR, IZMIRAN.
C - 36
FORECASTING OF 6 foF2 -VARI ATI ONS FOR IONOSPHERIC DISTURBANCES
V. P. Kuleshova, E. V. Lavrova, L. N. Lyakhova
Institute of Terrestrial Magnetism
Ionosphere and Radio Wave Propagation of
the Academy of Sciences of the USSR
Moscow, Union of Soviet Socialist Republics
Different types of ionospheric disturbances are distinguished.
The regular variations (Dst and SD) of 6 foF2 for each type are
derived. A good agreement between (Dst+SD) with real 6 foF2
changes during ionospheric disturbances is obtained. These regu-
lar variations of 6 foF2 are presented in the form of Dst and SD
maps, and the application of these maps to short-term forecasting
is recommended.
It is well known that every individual ionospheric disturbance has its
own peculiar behavior (Kane, 1973)- Nevertheless, the study of mean distur-
bance patterns continues to attract attention, both for disturbance-
predicting needs, as well as for studying physical causes of disturbances.
One of the methods used is to distinguish disturbance storm-time (Dst) and
solar local time (SD) variations from the observed value of 6 foF2. In
most early studies (e.g., Matsushita, 1959), the Dst and SD-var iations were
obtained for magnetic storm periods. Because of the variety of ionospheric
disturbances, the resulting Dst and SD variations were very small and the
irregular (Dl) part was dominant. The purpose of the present paper is to
distinguish regular components of 6 foF2 variations in such a way that they
include the most typical variations of 6 foF2 during ionospheric disturbances
connected with magnetic storms.
As a first step, the most typical ionospheric disturbances were
d i st ingu ished :
1. Negative disturbances with one active period, D, ;
2. Negative disturbances with several active periods, D_„ ;
3. Two-phase disturbances (the initial phase a positive
d i sturbance) , D ;
A. Negative disturbances in night hours only, D
-n
5. Unstable state of ionosphere (the mixing of positive and
negative 6 f oF2 , D . ; and
mix '
6. Positive disturbances, D
+
C - 37
In contrast to the paper by Mednikova (1957) where ionospheric distur-
bances were picked out without taking into account geomagnetic activity, the
present paper deals with some additional types of ionospheric disturbances.
The ionospheric disturbances have been divided into strong (|6foF2 | >. 30%)
and weak (|6foF2 | < 30%), and into SC and GC , depending on the character of
geomagnetic storm commencement (sudden or gradual). The distribution of the
disturbances according to season has shown that the dominant types of distur-
bances are characteristic of different seasons. Thus, D_i and D_2 ionospheric
disturbances are dominant during the equinoxes, when they are observed with
a probability of 84% during large SOtype geomagnetic storms; in winter, all
types of ionospheric disturbances have almost equal probability.
The Dst (6 foF2) and SD (6 foF2) variations have been determined for the
dominant types of ionospheric disturbances of each season. In calculating the
Dst (6 foF2) variations, the duration of each storm was taken as the unit time
period for that storm. So the horizontal axis in figure la is divided into storm
parts rather than in hours. Figure la, b present examples of the resultant SD
and Dst variations for the most frequently observed type (D_]) found during
equinox months (solid curves). Figure la, b have for comparison the same varia-
tions obtained for periods of magnetic storms (dotted curves), as calculated
by previous authors (Matuura, 1972). The regular variation of 6 foF2 is thus
readily seen to be increased essentially by calculating SD and Dst variations
for different types of ionospheric storms.
-)st(gf.F2),ft The resultant SD and Dst variations can be
made use of for 6 foF2 forecasting during
disturbances. Figure 1c shows the real 6 foF2
during the disturbance of April 20, 1970
n (points) and the forecast of the storm
(Dst+SD) -var iat ion (solid curve). The mean
square difference between these variations is
± 7%. For all storms considered, the mean square
difference per storm fluctuates between ±5%
and ±15%.
For forecasting purposes, one must know
5 the expected onset time of an ionospheric
disturbance. Present research has shown that
the delay time of an ionospheric disturbance
onset (the steady decrease of 6 foF2 to - 15%
and more) in Moscow, with respect to the
£ magnetic storm onset, is determined by the
local time of the magnetic storm's main phase
onset (MPO) . The delay time is small (0-2
hou^s) in the evening and at night. In the
daytime it has a linear dependence given by
A Tm = 17-2 - 0.8 Tm, where A Tm is the delay
time (in hours) of the ionospheric disturbance
onset from the magnetic storm's main phase on-
set, and Tm is local time of the MPO.
QO Q2 M Q6 QJB 10
5D».F2# Stonm parts
15 20 0
20.M.70
Figure 1 . (a) Dst (6 foF2)
and (b) SD (6 foF2) vari-
ations for D_j iono-
spheric disturbances in
equinox; (c) (Dst+SD) and
real 6 foF2 for 20.0^.70
storm (see text) .
It is natural to expect that for different
types of ionospheric d i s turbances, the preceding
solar-terrestrial conditions have to be taken
38
into consideration. But in spite of some differences in the distribution of
ionospheric disturbance types with respect to solar characteristics (see
Figure 2, where (1) denotes disturbances connected with flares, (2) with
recurrent active regions and (3) with new regions), it is evident that the
observable solar characteristics are not the only cause of different
ionospheric disturbances types.
It can be supposed that just as is the case with the fine structure of
magnetic disturbances (Ivanov, 197*0, so is the character of the ionospheric
disturbance determined by the structure of interplanetary magnetic fields
and by their interactions with the Earth's magnetosphere . This assumption
is confirmed by comparison of the ionospheric disturbance development with
geomagnetic variations. For example, the D_| type is observed for the case
of a very well developed main phase immediately after the SC of a magnetic
storm, while the D_n type is associated with large delay times of the main
phase onset relative to its SC.
Results of the present analysis demonstrate that the types of iono-
spheric disturbances are connected mostly with the development of the main
phase of a magnetic storm, which is itself determined by the structure of
the solar wind and by its interaction with the magnetosphere.
The dividing of ionospheric disturbances into types and picking out
regular variations help in the estimation of the contribution of individual
processes which lead to ionospheric disturbances. There are, for example,
some hypotheses (Matuura, 1972) about the cause of SD- (ionospheric currents
in the polar region) and Dst-var iat ions (changes of atmospheric composition
due to global convective motion).
%
100
m
o
t
fc^
V% B-n
HDD Bm;«
■ D*
Figure 2. Distribution of iono-
spheric disturbances types
depending on hel iophys ical situa-
tion: 1-flares; 2-recurrent ac-
tive regions; 3-new active regions
The irregular Dl-variation can
be interpreted as the superposition
of the different oscillations
associated with individual processes.
The contribution of these oscilla-
tions can be different for each
individual disturbance.
Preliminary research on the
spectral composition of the iono-
spheric Dl-variation showed that the
observed maximum of the spectrum
occurred in the frequency range
0.33-0.38 hr-1 (period about 3
hours); for some storms this is
identified with a similar maximum in
the AE index spectrum. This indi-
cates that an auroral electrojet
intensity change gives a contribu-
tion to the Dl-variation.
The calculated regular storm
variations for ionospheric stations
39
Dst(ff.F2),%
bwrwer,5C
w ao ai 0.2 Q3 oa as o£ 0.7 0.8 0.9 uo
storm parts
SD0f.F2),% 5ummer,SC
> J^"' » „ g V
w\ \"» — -= ' • — ^
,°.
20
~'>'5^ / 1 L \-L 1 -
of different latitudes in the eastern
hemisphere can be presented in the
format of maps of SD- and Dst varia-
tions for the dominant types of
ionospheric disturbances. Figure 3
shows examples of Dst and SD maps for
ionospheric disturbances of the D_i
type in summer.
By means of these maps, it is
possible to prepare a forecast of the
development of an ionospheric distur-
bance (it is, of course, necessary
to know the real or predicted onset
of the magnetic storm main phase).
The mean-square error of such a fore-
cast is ± 15%. This error is the
mean irregular (Dl) part of ionospheric
disturbance.
Figure 3- Dst and SD maps for D_j
ionospheric disturbances in
summer.
REFERENCES
Ivanov, K. G., and N. V. Mikerina (197*0: Composition of the interplanetary
plasma stream and the magnetospheric storms. In: Solar Wind and Magne-
tosphere, Moscow, USSR Academy of Sciences, 3-
Kane, R. P. (1973): Global evolution of F2 region storms. J. Atm. Terr.
Phys., Vol. 35, Nl , 1953-1966.
Matsushita, S. (1959): The study of ionospheric storms morphology.
J. of Geophys. Res. , Vol. 64, N3.
Matuura, N. (1972): Theoretical models of ionospheric storm. Space Sci .
Revs., Vol. 13, Nl , 124.
Mednikova, N. V. (1957): Ionospheric disturbances in middle latitudes.
I n: Physics of solar corpuscular flows and their influence on the upper
atmosphere, reports of the Conference of Committee on Investigation of
Sun, 1955, 22-24 XI, Moscow, USSR Academy of Sciences, 1 83 .
C - 4o
FUNDAMENTALS OF THE PHYSICAL
FORECAST OF IONOSPHERIC PLASMA
M. N. Vlasov
Institute of Applied Geophysics
USSR Goscomgidromet
Moscow, USSR
A new method of forecasting the ionospheric plasma based on
a physical model is considered. The physical forecast must solve
two main problems simultaneously: the prediction of the iono-
spheric parameters that determine radiowave propagation of
the prediction of the parameters that influence the flight of
cosmic objects. There are two main requirements for the physical
forecast: first, the forecast must include the results of cur-
rent investigations of ionospheric plasma physics, and second,
a common physical basis of the plasma forecast and of the
meteorological forecast is necessary because of the strong
coupling between the upper and lower atmosphere. The system
of hydrodynamic equations is considered as the basis of the
physical forecast of the ionospheric plasma. The theoretical,
empirical, and semi-empirical models of the ionospheric plasma
are discussed with a view to using these models for the physical
forecast. It is shown that the self-consistent theoretical
model based on the hydrodynamic equation system may be used for
the physical forecast of the ionospheric plasma at middle lati-
tudes. The main advantage of the model is the self-consistent
description of the behavior of the neutral and charged constit-
uents. Analysis of the preliminary results of the ionospheric
forecast based on the self-consistent model indicates that the
theoretically calculated parameters of the radiowave propagation
are very close to the values deduced from vertical-incidence
sounder data. The development of theoretical models of the
ionospheric plasma in the future is discussed.
Recently the development of ionospheric and upper atmospheric investiga-
tions has made possible the detailed theoretical description of ionospheric
plasma behavior. A comprehensive study by Stubbe (1970) attempted, for the
first time, the simultaneous theoretical treatment of the neutral and charged
constituents, and thereby constructed a realistic ionospheric model. At
present, a number of ionospheric models are available (Polyakov et al. , 1975;
Namgaladze et al . , 1972; Kolesnik, 1976; and Vlasov and Kolesnik, 1979). The
comparison of these models with experimental data indicates that the main
features of the ionosphere are reflected in detail by these models. Recently,
C - k]
attempts at the creation of two- and three-dimensional models have been made
(Straus and Schultz, 1976). The successful theoretical description of the
ionospheric plasma appears to be necessary for use in current ionospheric
forecasting.
The forecast has two main purposes: prediction of those ionospheric plas-
ma parameters that determine radiowave propagation, and prediction of the •
parameters that influence flights of cosmic objects. The parameters of the
first group are mainly connected with charged particles and the parameters of
the second group are connected with neutral components of the ionospheric
plasma. All current investigations indicate a very strong coupling between
neutral and ionized species. The close connection between neutral and ionized
species is due to the photochemical processes of production and loss of neu-
tral and charged particles by the dynamical transport processes, e.g., the
drift charged particles induced by the neutral wind and electrodynamic drifts
of neutral particles induced by collisions with ionized species. This means
that the two main problems of the ionospheric plasma forecast must be solved
simultaneously by using theoretical models.
The purpose of this paper is a discussion of a new method of ionospheric
plasma forecasting based on the physical models. The statistical ionospheric
forecast based on vertical-incidence sounder data does not satisfy modern
practical demands. First, information about the height distribution of elec-
tron density is necessary for predicting radiowave propagation, but this in-
formation cannot be deduced from vertical-incidence sounder data. Also, in-
formation about the electron and ion temperature is very important and these
parameters cannot be deduced from sounder data. Second, a statistical fore-
cast has all the disadvantages characteristic of a statistical description
of a variable phenomenon. Third, it is impossible to include modern iono-
spheric plasma physics in the creation of a physical forecast.
The development of a new method of ionospheric forecasting based on a
physical model of the ionospheric plasma may overcome many of the above-men-
tioned difficulties. Recently a physical model based on the hydrodynamic
description of air motion in the lower atmosphere was developed for forecast-
ing weather. Taking into account the close relationship between the upper
and the lower atmosphere, it is very desirable that physical models for fore-
casting the ionospheric plasma and the weather be based on the same theoret-
ical fundamentals. The hydrodynamic treatment may be used for describing
the behavior of the lower atmosphere as well as - the upper atmosphere (below
400-500 km). In this case, the physical model of the ionospheric plasma is
similar to the hydrodynamic model of the meteorological forecast. Due to
this common basis, our understanding of the relationship between both models
may be developed in the future.
The difference between the hydrodynamical description of the lower at-
mosphere and magnetohydrodynamical description of the ionospheric plasma
is very significant. The main difference is that in the ionospheric plasma
the elementary processes as well as the collective processes are important
but the behavior of the lower atmosphere is controlled only by the collective
processes. Electromagnetic forces play an important role in the ionospheric
plasma but these forces are neglected in the lower atmosphere. The principal
problem of the lower atmosphere is the description of the atmospheric gas in-
teraction with the ground surface.
It is clear that the modern ionospheric plasma description based on the
solution of the hydrodynamic equation system might not present the total pic-
C - 42
ture of the behavior of the neutral and charged constituents for different
conditions. First of all, we assume that this description is very comprehen-
sive for the middle-latitude ionospheric plasma under undisturbed conditions.
For other conditions, the coupling between the ionosphere and magneto-
sphere is very important and in this case, the theoretical description becomes
very difficult. We do not have any realistic theory which describes the iono-
sphere-magnetosphere coupling. Therefore, the self-consistent theoretical de-
scription of the ionospheric plasma may be developed in detail only for the
middle latitudes for undisturbed conditions. The hydrodynamical equation
system, by characterizing the neutral and charged constituents of the iono-
spheric plasma for different levels of solar activity, may be used to predict
the diurnal, annual, and semiannual variations of the height distribution of
the main parameters.
It is necessary to emphasize that this theoretical description does
not require additional information about any parameters of the plasma. The
boundary conditions may be induced from the measured data but this fact does
not violate the theoretical description when the behavior of the plasma about
these boundaries is not represented by the theory. Consequently, the iono-
spheric plasma model based on this self-consistent theoretical description
may be named the theoretical model. By contrast, there are semi-empirical
ionospheric plasma models in which a number of the plasma parameters are
given by experimental data.
In most of the semi-empirical models, the parameters connected with the
neutral atmosphere are given by experimental data but the parameters of
ionized constituents are theoretically calculated. However, there is a set
of models in which parameters of the charged particles are given by measure-
ments. These plasma parameters are the electron and ion temperatures.
The determination of ionospheric parameters from experimental data makes
it possible to eliminate a number of theoretical equations. However, in this
case , agreement between the parameters given by experimental data and the
parameters deduced from theory may be obtained only by using different in-
dexes. It is known that the indexes represent the ionospheric plasma state
very roughly but are not self-consistent with the semi-empirical models.
First of all, in the semi-empirical model, the parameters of the
neutral atmosphere do not agree with the ionospheric parameters , and con-
sequently, in this model, the connection between the neutral and ionized con-
stituents is violated. In spite of the improvement of the empirical models
of the neutral atmosphere resulting from a large number of satellite measure-
ments, these models do not reflect a number of features of the upper atmo-
sphere and there is no agreement between them (Hedin et al. , 1977; and Bar-
lier et al., 1978). The creation of an empirical model of the neutral at-
mosphere reproducing all variations is impossible because of the enormous
number of measurements necessary. Therefore, whenever it is possible, we must
construct the semi-empirical and theoretical models of the neutral atmosphere
because this model may be in best agreement with the ionospheric model.
The theoretical model of the ionospheric plasma is the best generaliza-
tion of the experimental data. Whenever the relationship between the neutral
and charged constituents is very important, the self-consistent theoretical
model of the ionospheric plasma must be developed.
However, it is clear that, at present, only a semi-empirical model may
be constructed to describe the polar ionospheric plasma as well as the dis-
turbed ionospheric plasma for middle latitudes and the equatorial latitudes.
C - A3
An empirical ionospheric model based on available satellite, rocket, and
ground-based measurements may be applied to ionospheric forecasting, but in
this case the forecast is statistical. However, innumerable measurements
are necessary for the empirical description of the ionospheric plasma (Nisbeth,
1975) .
For the development of the physical model, the empirical models are very
necessary, first of all, for the comparison of the theory with the measure-
ments, and for the improvement of the theoretical model. The main purpose of
the experimental investigation of the ionospheric plasma is to reveal and to
study the plasma features which are important for the construction of the
self-consistent theoretical models. Therefore, the difficulties of the theo-
retical description must determine the direction of the experimental inves-
tigations.
For estimation of the physical forecast, the self -consistent time-depen-
dent model based on the solution of the coupled momentum, energy balance, and
continuity equations has been developed. This model is discussed in the paper
by Vlasov and Kolesnik (1979) , where the comparison with the experimental data
is presented. Only the ionospheric forecast parameters deduced from the model
are considered. The plasma frequency, foF2, has been computed from the self-
consistent model and compared with the vertical-incidence sounder data. The
comparison has been made for a number of ionospheric stations at middle lati-
tudes: Ashkabad, 37.9°N; Boulder, 40°N; Alma-Ata, 43.5°N; Tbilisi, 41.7°N;
Irkutsk, 52°N; Tomsk, 56.5°N; Moscow, 55.6°N; Sverdlovsk, 56.7°N; and Monte-
Capellino, 44.5°N.
For these stations, the discrepancy between the theoretical plasma fre-
quency and the vertical-incidence sounder data is about 20 percent in the
daytime. However, the discrepancy increases in the twilight and nighttime.
The description of the variation of ionospheric parameters at twilight is a
very complex problem.
The theoretical height distributions of the electron density and the
values of hmaxF2 have been compared with the incoherent scatter data from
Millstone Hill (Evans, 1975) and the vertical-incidence sounder data from the
ionosphere stations. The theoretical profiles are in good agreement with the
experimental data. Thus, the primary results indicate that it is possible to
create a physical model based on the self-consistent time-dependent model of
the ionospheric plasma and this model can predict the behavior of the neutral
and charged constituents.
However, the creation of physical hydrodynamical forecasts of the iono-
spheric plasma is a very difficult problem and it requires the development of
ionospheric models. Three main aspects of the development of the self-con-
sistent theoretical models may be pointed out. First, the two-dimensional
model is necessary for the calculation of the neutral wind that influences
the ionospheric plasma behavior at twilight and nighttime. Second, the ex-
cited species processes are necessary to take into account the calculation of
the energy balance of the ionospheric plasma because the excited species
store a very considerable amount of energy and then transfer the energy to
the ambient gas. For example, it is evident now that the vibrational tem-
perature of the ionospheric plasma is an important parameter as well as the
electron, ion, and neutral temperatures (Vlasov, 1976). The excited species
processes play an important role in the explanation of the winter anomaly
(Vlasov and Izakova, 1979) . Thirdly, the development of the model of the
ionospheric plasma of the lower thermosphere and mesosphere is very important
due to two reasons: this model may be used as the lower boundary condition
C - kk
for the self-consistent model, and may be useful for understanding the rela-
tionship between the upper and lower atmosphere. The main problem of this
model is the eddy diffusion transport. It appears that a number of experi-
mental investigations and further development of the theory are very necessary
for resolution of this problem.
As for the experimental investigations of the upper atmosphere, the vi-
brational temperature measurements are necessary. Unfortunately, we do not
have direct methods for measuring this parameter. An indirect method of de-
termining the vibrational temperature is based on the mass-spectrometric
measurements of the air release in the upper atmosphere (Danilov et al . , 1977),
Summarizing all the above, the following main conclusions may be drawn:
1. At present an ionospheric plasma forecast is necessary to resolve
two main problems: the prediction of the variations of the plasma parameters
that determine radiowave propagation and the prediction of the parameters con-
trolling the satellite flights. The resolution of these problems requires a
detailed description of the spatial and temporal variations of the ionospheric
plasma parameters. The statistical forecast cannot resolve these problems.
2. Resolution of this forecast problem is possible only by using physi-
cal models of the ionospheric plasma. In this case, the model is based on the
hydrodynamical equation system that describes the behavior of the neutral and
charged constituents.
3. The relationship between the upper and lower atmosphere can be taken
into account if the meteorological forecast and the ionospheric plasma fore-
cast are based on the same conception. The hydrodynamical treatment must de-
scribe the behavior of the upper and lower atmosphere so far as the ionospher-
ic plasma physical forecast may be connected with the meteorological hydro-
dynamical forecast that is developed at present.
4. In contrast to the statistical forecast, the physical forecast based
on the self-consistent time-dependent model of the ionospheric plasma can in-
clude modern and future advances of ionospheric physics.
5. The primary results indicate that the semi-consistent model may be
used for the physical forecast of the ionospheric plasma. The plasma fre-
quency deduced from the model is in very good agreement with the vertical-
incidence sounder data at middle latitudes.
6. The main problems of the theoretical modelling for the forecast are
the following: the development of a two-dimensional model; the inclusion of
the excited species processes; the construction of the model of the lower
thermosphere and mesosphere as the low boundary condition for the self-con-
sistent model.
It should be emphasized that the problem of the physical hydrodynamical
forecast of the ionospheric plasma is very complicated and international in-
vestigations of it would be desirable.
REFERENCES
Barlier, F., et al. (1978): Ann. Geophys., 34:9.
Danilov, A. D., et al. (1977): COSPAR Space Res. , 17:465.
Evans, J. V. (1975): Millstone Hill Thompson Scatter Results, Tech. rpt. 513.
Hedin, A. E. , et al. (1977): J. Geophys. Res. , 82:2139.
Kolesnik, A. G. (1976): V sb. "Fizika ionosfery," M. , Nauka, s. 139.
C - *45
Namgaladze, A. A., C. S. Latyshev, and M. A. Nikitin (1972): Preprint IZMIRAN,
N. 7, Moskova.
Nisbet, J. S. (1975): Atmosph. Earth and Planets, Proc. Summer Adv. Study,
Dordrech, Boston, 245.
Polyakov, V. M. , M. A. Koen, and G. V. Hazanov (1975): V sb. "Issledovaniya po
geomagnetizmu, aeronomii i fizike Solnza," vyp. 33, 9.
Straus, J., and M. Schulta (1976): J. Geophys. Res. , 81:5822.
Stubbe, P. (1970): J. Atmosph. Terr. Phys., 32:865.
Vlasov, M. N. (1976): J. Atmosph. Terr. Phys., 38:807.
Vlasov, M. N., and T. M. Izakova (1979): COSPAR Space Res. , 19 (submitted).
Vlasov, M. N. , and A. G. Kolesnik (1979): Paper presented at this workshop.
C - k6
SELF-CONSISTENT MODEL OF THE IONOSPHERIC PLASMA
AND THE HYDRODYNAMIC FORECAST
M. N. Vlasov
Institute of Applied Geophysics, Goskomgidromet of the USSR
Moscow, USSR
and
A. G. Kolesnik
Tomsk University, the USSR Academy of Sciences
Tomsk, USSR
The system of hydrodynamic equations has been used to con-
struct a self-consistent theoretical model. In the model, the
simultaneous behavior of the neutral and charged constituents is
described. A self-consistent model of the ionospheric plasma has
been made for the height region from 120 to 500 km at middle lati-
tudes. The comparison of the theoretical model with experimental
data and empirical models indicates a good agreement. The theo-
retical model reflects well the annual, semiannual, and diurnal
variations of the ionospheric plasma. This indicates that the
model may be used for the forecast of ionospheric plasma
parameters. The maximum discrepancy between the plasma fre-
quency deduced from this model and obtained from vertical in-
cidence sounding data is equal to 20 percent in the daytime.
Vlasov (1979) has suggested a new method of forecasting the ionosphere
and upper atmosphere based on a physical model of the ionospheric plasma
processes.
According to Vlasov (1979), this method may be based on the ionospheric
plasma model produced by the solution of the hydrodynamic equation system
for the neutral and charged constituents. This model can be developed to
forecast disturbed conditions at middle latitudes.
The purpose of this paper is to present a self-consistent theoretical
model of the middle latitude ionospheric plasma from 120 to 500 km and to
estimate the forecast possibility of this model.
I. BASIC EQUATIONS AND PROCESSES
The total equation system of the model includes the continuity equations
C - hi
JT ■«■■ ' l; -fl7("iwi»; ' -*. ••• '<> (')
where n j is the concentration of 0 , 02 , NO , N2 , N(4S) , NO, N(2D);
i = ^, 5, 6, 7, 8, 9, 10, respectively; wj is the vertical component of the
ith partial velocity which is supposed to be equal to zero for i = 5~ 1 0 .
For the 0+ ion,
W* = -Da^'^ + T^ + ^ sinM - u„ s.n I cos I (2)
where Da is the ambipolar diffusion coefficient; I is the geomagnetic declin-
ation; ne = Znj (i = k, 5, 6, ... 10) is the electron concentration;
T = Tg + Tj; Hp = kT /mi+g; and un is the meridional component of the neutral
gas velocity.
The ion product ion and transformation rate (qj) and the loss rate {l\)
are determined by the following photochemical processes:
(a) the ionization and dissociation by solar radiation
0 + hv -> 0 + e~; N2 + hv -> N2 + e
02 + hv •*■ 02 + e"; NO + hv -> N + 0
(b) ionization and dissociation by photoelectrons
+ +
O + e^+O +e; N2 + e^-* N2 +e
02 + e^ -»■ 02+ + e; N2 + e^-> N(4S) + N(2D)
(c) ion-molecule reactions
0+ + N2 + N0+ + N(4S); 0+ + 02+ + 02+ + 0
02+ + NO •*■ N0+ + 02; N(4S) + NO ■*■ N2 + 0
(N0+ + N(4S); N2+ + 02 + 02+ + N2
N2 + 0 -H
VNO + N(2D); N(2D) + 02 -> NO + 0
(d) dissociative-recombination reactions
r<>(3P)+0(lD) (N(2D)+0(3p)
02 + e+loI'D) + 0('d); NO + e * <
lo(3P) + 0(*P) KS) + °(3P)
fN(2D) + N(2D)
N2 + e -M
Ln^S) + H{kS)
This scheme of the ionospheric processes corresponds to that of Danilov
and Vlasov (1973). The calculations of photoelectron spectra and ionization
rates are from Kolesnik and Chernishov (1978). The change of ultraviolet
radiation spectrum (X < 1027A) with solar activity is taken from Chernishov
(1978).
The distributions of the main neutral components are determined from
the barometric law z
2S^H (-/ «1), c-I, 2, 3 (3)
a rn z0 "a
C - k8
where a = 1, 2, 3 for 0, 02 , N2 , respectively; and Ha = KTn/mag. A very im-
portant part of the total system is the equation for heat balance of the iono-
spheric plasma. The equation for the neutral temperature is
aT 3^T 3 A 3T
nn^P ?T = Xn -g^T + Ijr ~ nncp (WB + W-,)] ^ - mnnngWn + Qn - Ln (k)
where 3 ,3 _ , 3
n„ = y n > m = — y m n , c = — V c^n, ,
n L. a* n n L. a a' p n ^ pa a '
a=l n a=l n a=l
An is the heat conductivity according to Banks and Vockarts (1973) i Qn and Ln
are the local heating and cooling rates, respectively, of the neutral gas ac-
cording to Kolesnik and Chernishov (1978)', Chernishov et al . (1978), and
Stubbe and Warnuum (1972); W„ and Wn are the vertical components of the
neutral gas drift due to the "breathing" of the atmosphere and the horizontal
wind divergency are equal, respectively, to
WB = Tn J T^FTdz' (5)
z0 n
WD=W Ifc <Vn> ♦ ^ (nnUn)ldz. (6)
n z '
according to Rishbeth et al. (1969). The X- and Y-axes are coincident with
the zonal and meridional directions, respectively; and Vn and Un are the
zonal and meridional components of the neutral gas velocity.
The equation for the electron temperature is
3Te „ 2 *e 92Te 2 3Xe 3Te 2 Te 3n( _
3t 3 <nQ dzz + 3Knp 3z 3z + 3 np St T 3i<np v^e " V
•e
+ ( (7)
i <j t- ails ■ la o «■ o *- j i ia a i. »»i^i'p
where Xe is the electron heat conductivity as given in Banks and Kockarts
(1973) ;k is Boltzman's constant; Qe and L are the local heating and cooling
rates, respectively, of the electron gas (Kolesnik and Chernishov, 1978;
Chernishov and Kolesnik, 1978; and Stubbe and Warnuum, 1972). For the 0_e and
Qn calculations, the intensity of the Schuman-Runge radiation and the 02 ab-
sorption cross section according to Ackerman (1970) are used.
Neglecting the heat conductivity in the heat balance of the ion gas, the
T- equation may be presented in the form
Ti = (Tn + eTe"1/2)/(l + eTe"3/2) (8)
9 = 1.7 • 10s n T "1/2/n
en / n
where
In our model, the equations for the zonal and meridional components of
the neutral gas velocity are (Gerschman, 197^; and Geisler, 1966) :
3Vn
3t
- Ha
" Pn
32Vn
3z^ '
1
Pn
3Pn
9x
8Un
3t
- Ua
" Pn
82Un
3z^ "
1
Pn
9Pn
3y
2fiUn sin cj> - — v. V sin2 I (9)
n T nn in n
•n
" 2fiVn sin * ■■ — vinUn (10)
c - ks
where fi is the Earth's rotation velocity; Un is the molecular viscosity co-
efficient; p n = m_n • P_ is the pressure; and v. is the ion-neutral col-
li n n n ■ in
1 i s ion frequency .
The values of 3Pn/3x and 3Pn/3y are calculated using the 0G0-6 model
(Hedin et al., 197*0- The initial conditions are given by the periodical
solution of U(t) = U(t + T) , where T = 2k hours.
At the lower boundary (zo = 120 km), the 0, O2, N2 concentrations are
given by an empirical model (Kolesnik, 1975); the 0 concentration is given
by equation (l) for wi+ = 0; the electron temperature is found from equation
(7) neglecting heat conductivity (^e = 0) ; the neutral temperature is ac-
cording to the 0G0-6 model (Hedin et al., 197*0; the Vn and Un values are
taken to be zero. At the upper boundary (z^, = 500 km), the 0 flux is given
by Thompson scatter measurements (Evans, 1971a, 1971b, and 1975); the elec-
tron temperature is given as the gradient 3T /3z, using the results of Evans
(1975, 1967, 1971c, and 1970). A neutral temperature condition is taken as
3Tn/8z = 0, and the Vn and Un condition is (3Vn/3z) = (3'Jn/3z) = 0.
Equations (l) through (10) are solved by the numerical method and the
calculation of photoelectron spectrum and the local heating are included.
MODEL AND EXPERIMENTAL DATA
The results of the calculation of the main plasma parameters are com-
pared with the satellite and experimental rocket data and ground-based mea-
surements. Figure 1 gives a comparison of the calculated atomic oxygen con-
centration using both the theoretical model and the empirical model (Kolesnik,
1975) and with the CIRA-72 model.
Good agreement between the theoretical prediction and the empirical
atomic oxygen concentration (Kolesnik, 1975) is shown in Figure 1. However,
the atomic oxygen concentration from the CIRA-72 model at the height of
150 km at equinox is three times higher than the concentration from the
theoretical model, but at a height of 200 km, the calculated concentrations
are smaller than the concentration from the CIRA-72 model by a factor of 2-3.
The discrepancy for the concentration of O2 and N2 is smaller. Differences
between the CIRA-72 model and a number of experimental data are well known
and have been discussed (Mikhnevich et al., 1976; and Tricke et al., 1976).
Figure 2 shows the variations of the neutral gas temperature with solar
activity. The temperatures Tn max and Tp m- are maximum and minimum temper-
atures of the diurnal variations (r = Tn max/Tn min)- The values of Tn mjn
and r deduced from the satellite drag data XRoemer, 1971) and calculated by
Stubbe (1970) are given in Figure 2 for the latitude <J> = 52°N at equinox.
The variations of Tn max and T • with solar activity agree well with ex-
perimental data (Waldteufel and Coggen, 1971). The winter increase of Tn max
with solar activity is smaller than in summer due to the very significant
role of the Schuman-Runge continuum radiation in the winter heat balance. A
similar result has been obtained by Kolesnik (1976) for a stationary model.
Figure 3 shows the diurnal variation of Tn at equinox deduced from the
theoretical model. For comparison, the OGO-6 data, Stubbe's model (1970),
and the Thompson scattering results (Evans, 1975; Salach and Evans, 1973)
are also presented in Figure 3.
C - 50
^^o^ooooooooooooooooooooooooooooo ^poooocoooocPoooooOOooooooooooocoo^0000ocooooooooooooooo00o000oooc
k\
*xxxxxxx*xxxxxxxxxxxxx >
z
200K/T1
oooooo F/Q?-20Q\ mode?
3o ooooo oooooooooooooooooooc >
x<^x < x, x.x.y^^xx.xx.xx x,x.x,^xx
150 ^m
, <xXx! WXXxTTxxxxxxxxxxXx
200 km
¥=J5°
xxxx _ ZoCtsnik.
xx x x x'x'xx' x x x x xxxxx'x'x xxxXxj
ISOxm
.x.ooooocaooooo^ojoooooooooooooo
200*m
Vyr^x'x,xVx',>;^VxxxV^xfe<:«xx^x:xx
/JO*/??
>OOOOOOOOOOOOOOOOOOOOOooooo°OOOOoO
JOOOOOCOOOOO,-,^^ . i_— • — . _7^^ooc> yoooooCKXJ OOOOOO'-' """""^POOQOOO OOP u
' I . ■ ■ ■ ■ II ' ■ ■ 1 i i lr- i* — i *"**'
'00 04 06 12 Iff 20 24'0 04 OS 12 16 20 2410 04 06 12 Iff 20 2i
LT LT LT
Figure l. The diurnal variation of 0 concentration at
height l 50 km and 200 km.
The Tn latitude variation is about 130° K for the latitude range from
40°N to 55°N and this variation depends on season. In winter, the value of
Tn for hO°H is higher than the value for 55°N at equinox. This latitudinal
discrepancy decreases at equinox and is neglected in summer. Similar results
have been deduced from the AEROS-A satellite data (Rawer, 1976).
In our model the time of the daily maximum of the neutral temperature
is two hours after the time of maximum in the experimental data. This fact
may be connected with a one-dimensional approximation (Baily and Moffett,
1972; Straus et al. , 1975) .
The theoretical and experimental height distributions of Te and Tj are
given in Figure h. The comparison of the theoretical height profiles of Te
with the incoherent measurement data (Evans, 1970) indicates good agreement.
For high solar activity, the maximum of the theoretical electron temperature
appears at an altitude near hmaxF2. This effect has been observed by Bauer
(1976) and may be explained by the energy transfer to ions. Thus the elec-
tron and ion temperatures calculated in the model are reliable for different
ionospheric conditions.
Figure 5 shows the plasma frequency variation with height, season, and
solar activity at latitudes <J> = 55°N and <J> = 70°N. There are annual and semi-
annual variations. Figure 5 illustrates the behavior of the winter anomaly
in the F2 region and the hmaxF2 variations and a number of other features.
Therefore the comparison of the theoretical model with experimental data
and empirical models (MS I S model, CIRA-72 model) indicates that this self-
consistent model reflects the main features of the ionospheric plasma be-
51
12S0
SOO
400
/SOO
7400
7000
fi/tn
7, SO
1.S0
i.40
7.J0
f.20
1200
0~=70
S~=2J°
o Stojie 1370
I n mat . K
mat ,
Tnmrn
60 50 700 720 /40 700 760 200
SOO
o5/r
-Hedin,etat[7SP4] StuSSe [1970]
o Evans [1071] — *sSM\A/ffd,/
00 04 08 72 70 £9 24 LT
Figure 2. The neutral temperature Figure 3- Diurnal variation of
variation with solar activity. neutral temperature.
?0
\
f«2?
400 1200 2000 2800
400 /200 2000
70
?0
4€0 /200 2000
Figure k. Height profiles of electron and ion temperature,
C - 52
hhihaSad
i i ^-= — =»» ■ — ■-■ ■ ■ — ■ — — ^ -~ — ■ — ■ — ■ — ■ ■ ■ — — ■
00 04 OS fZ fS 20 00 04 OS f2 fS 20 00 04 06 tZ Iff 20 Ot
Figure 5. Plasma frequency variations.
i ft m/t t urn
y=37,09
r£.°°0O
MHZ
fZM
fQ0&t> ■
<w4o
3ou?dez
fff.SS.SS
y=sff.0'
000° cP0ooo
4M-
MM ■:
m fSMffi „
Monte Xapeteino
i/>=44tSa
MOM
a oo ov 0j a ,'g 20 2k oo ov 08 h h 20 3H
L>' LT
oo n 01 11 16 20 ULJOO CM, bt h k io
Figure 6. Comparison of the frequency Figure ~] . Comparison of the frequency
calculated from the model with vertical and hmaxF2 values deduced from the
sounder data for different ionospheric model with ionospheric station data,
stations.
C - 53
havior. It is very important that the model describes the simultaneous be-
havior of the neutral and charged constituents.
3. MODEL AND FORECAST
Calculations of foF2 from the model have been made and the values com-
pared with the vertical incidence sounder data of ionospheric stations.
For example, the comparison of the theoretically calculated values of
foF2 with the ionospheric data for the midlatitude stations in the north
hemisphere is presented in Figures 6 and 7-
Averaged values of foF2 were used for the comparison. Figure 7 shows
also the values of hmaxF2 in comparison with the incoherent scatter data
(Evans, 1967, 1970, 1971b). In the daytime the error of the forecast is
about 20 percent. The error increases greatly for twilight conditions. This
may be explained by the very strong influence of the upper boundary conditions
on the ionospheric behavior in twilight and nighttime. In the daytime this
influence is neglected. At nighttime and twilight the thermospheric wind
strongly influences the electron density height distribution but the wind
calculation is based on the horizontal gradients from the 0G0-6 model, which
are not reliable for this purpose.
k. CONCLUSION
The system of hydrodynamic equations makes it possible to construct a
theoretical model of the ionospheric plasma without including empirical
parameters. In this model, the simultaneous behavior of the neutral and
charged constituents is described. A self-consistent model of the ionospheric
plasma for altitudes from 120 up to 500 km at middle latitudes may be con-
structed. The comparison of the theoretical model with experimental data and
empirical models indicates good agreement. The theoretical model reflects
well the main features of the ionospheric plasma indicating that it may be
used to forecast ionospheric plasma parameters. The maximum discrepancy be-
tween the plasma frequency calculated from the model and deduced from verti-
cal-incidence sounder data is equal to 20 percent in the daytime. The de-
velopment of a self-consistent model is necessary to develop a physical
forecast of the ionospheric plasma.
REFERENCES
Ackerman, A. (1970): Aeronomica Acta, A, 77-
Banks, P. M. , and G. Kockarts (1973): Aeronomy, Academic Press, New York,
London.
C - 5k
Bauer, Z. (1976): FIzika nebesnikh atmosfer, Moscow, "Mir."
Bailey, G. T. , and R. T. Moffett (1972): Planet. Space Sci . , 20:1085,
Chernishov, V. I., A. G. Kolesnik, and M. N. Vlasov (1978): Geomagnetizm i
Aeronomiya , 18, 2.
Chernishov, V. I. (1978): Geomagnetizm i Aeronomiya, 18, 5.
CIRA-72, COSPAR International Reference Atmosphere, (1972): Academie-Verlag,
B e r 1 in,
Danilov, A. D. , and M. N. Vlasov (1973): Fotokhimiya ionizovannykh i
vozbyzhdenn ikh chastis v nizhnei ionosfere. Leningrad, Gidrometeoizdat.
Evans, J. V. ( 1 967) : Planet. Space Sci. , 15:1387-
Evans, J. V. (1970): Planet. Space Sci . , 18:1225.
Evans, J. V. (1971a): Radio Sci. , 6:843.
Evans, J. V. (1971b): Radio Sci . , 6:609.
Evans, J. V. (1975a): Millstone Hill Thompson Scatter Results 1968, Technical
Report 513, Millstone Hill, Massachusetts.
Evans, J. V. (1975b): Planet. Space Sci . , 23:1611.
Evans, J. V. and J. Holt (1971): Radio Sci. , 6:855.
Fricke, K. , et al. (1976): COSPAR Space Res., 16, 265.
Geisler, Y. E. (1966): J. Atmospher. Terr. Phys. , 28:703.
German, B. N. (197*0: Dinamika ionosfernoi plasmi, Moscow, "Nauka."
Hedin, A. E., et al. (197M: J. Geophys. Res., 79:215-
Kolesnik, A. G. (1965) : Geomagnetizm i aeronomiya, 15, 2.
Kolesnik, A. G. (1976): V sb. "Fizika ionosferi," Moscow, "Nauka."
Kolesnik, A. G. , and V. I. Chernishov (1978): Geomagnetizm 1 aeronomiya,
18, 1.
Mikhnevich, V. V., et al. (1976): V sb. "Sutochnie variatsii i korpuskuly-
arnoe izluchenie," L. Gidrometeoizdat, 119.
Rawer, K. (1976): Space Res. , 16:211.
Rishbeth, H., R. J. Moffett, and G. L. Wailey (I969): J,. Atmospher. Terr.
Phys., 31:1035.
C - 55
Roemer, M. (1971): Space Res. , 11:761.
Salach, I. E. , and I. V. Evans (1973): Space Res. , 13:268.
Stubbe, P. J. (1970): J. Atmospher. Terr. Phys. , 32:865.
Stubbe, P., and W. S. Warnuum (1972): Planet. Space Sci . , 20:1121.
Straus, T. , et al. (1975): J. Atmospher. Terr. Phys., 37:15z*5.
Vlasov, M. N. (1979): Proceedings of International Solar-Terrestrial Pre-
dictions Workshop Program, Boulder, Colorado.
Waldteufel, P., and L. Cogger (1971): J. Geophys. Res., 76:5322.
56
PREDICTION OF THE PARAMETERS OF THE MAXIMUM OF
THE VERTICAL ELECTRON DENSITY GRADIENT
T. A. Anufrieva, T. L. Gulyaeva, G. F. Kadukhin,
T. N. Soboleva, and A. G. Shlionsky
Institute of Terrestrial Magnetism
ionosphere and Radio Wave Propagation Academy of Sciences, USSR
142092, Troitsk, Moscow Region, USSR
The results of a study of the spatial and temporal variations
of the parameters of the maximum of the vertical ionization
gradient (height level, plasma frequency and the value of
(dN/dh)max) are presented. The corresponding prediction maps were
developed from N(h) profile data. It is possible to use planetary
maps of the critical frequencies and the F2 layer geometric
parameters for this purpose also.
1. GLOBAL DISTRIBUTION OF THE MAXIMUM HEIGHT GRADIENT
Available ionospheric predictions do not provide all of the data neces-
sary for predicting long distance radio wave propagation. For instance, there
are no data available on the inter-layer valley parameters and those of the
vertical ionization gradient maximum upon which the frequencies and the de-
termination of some waveguide characteristics by the extremal-parametric
method (Shlionsky, 1971) depend.
Model Ne profiles have been used in the present paper to analyze the
variations of (N'h)max parameters (Soboleva, 1972 and 1973; Kadukhin and
Soboleva, 1978a; and Rawer and Rama Krishnan, 1972) as well as electron den-
sity profiles calculated from vertical incidence ionograms (Kadukhin and
Soboleva, 1978b) using analogous searching methods (Kadukhin and Shlionsky,
1970).
The calculation of N(h) profiles from hourly ionograms has been carried
out for 13 stations: Huancayo, Talara, Bogota, Jamaica, Grand Bahama,
Wallops Island, Winnipeg, Col ledge, Churchill, Narsarssuaq, Godhavn, Resolute
Bay, and Thule. Equinox conditions (March) at solar activity minimum and
quiet geomagnetic activity have been considered: ^10. 7 = 75, ^z = ^» *^p = ®'
Figure 1 shows, in terms of geomagnetic latitude and local time, the
global distributions of the following parameters (the north and south hemi-
spheres are approximately symmetrical relative to the geomagnetic equator):
(dN/dh)max in the F region; the values of electron concentration, Ng; and the
heights at this point, hg.
C - 57
local time
H 8 12 16
20 2H
,c3 Jsoline of parameters 10 N«,e/cm (-)
h,,kmt— ;.
20 2*4
^soline of parameters (^ )max "10 cnv
•h e
C - 58
To investigate the changes in the parameters of gradient maximum these
data were complemented by empirical N(h) profiles, the latter being compiled
by generalizing the Ne measurements from rocket flights and those of the in-
coherent radio wave scatter method for two levels of solar activity:
(1) F10 7 = 75, Rz = 10, Kp = 0; and (2) F10.7 = 175, Rz = 100, Kp = 2 * 3-
Figures 2a and 2b and Tables 1 and 2 give the results of the compara-
tive analysis of (dN/dh)max values calculated from the different profiles:
the circles indicate the results of the N(h) profile analysis of ionograms
(Kadukhin and Soboleva, 1978b). The solid line shows the calculation from
the empirical model profiles (Soboleva, 1972, 1973) at solar activity minimum
for different hours of LT at $ = 50°N and along the noon-midnight meridian.
Numerical data obtained from both types of profiles fit well enough and
their relative changes are similar notwithstanding some differences in de-
tails. This allows us to study further the diurnal, latitudinal and cyclic
variations using only the empirical model profiles. The results for two
levels of solar activity and equinox conditions are shown in Figures 2c and
2d and in Tables 1 and 2.
The maximum values of daytime height gradients in the diurnal distribu-
tions of N^ax at middle latitudes (Figure 2c) are about twice as great as
those of the night hours, small extrema are observed at morning and evening
hours, the evening one being more distinct. A geomagnetic daytime anomaly is
observed in the latitude distribution of N^ax (Figure 2d), when the equatorial
values are smaller than those observed at $ = 20°N. The value of NrJiax de-
creases at high latitudes. The minimum values of the gradient are observed
near the trough latitudes at night similar to those of the F2 layer critical
frequencies while N^ax increases towards low latitudes.
As solar activity changes from F^q. 7 = 75 to Fjq 7 = 175, N^ax increases
on an average by the order of 1.5 times (Figures 2c, 2d, Tables 1 and 2).
Seasonal variations of the gradient maximum are tabulated in Table 3.
These are from the tentative table of Electron Density for Temperate Latitudes
(Rawer and Rama Krishnan, 1972). Noon and midnight for two solar activity
levels (Rz = 10 and 100) and for four months (March, June, September, Decem-
ber) have been considered. Maximum values of Nmax in daytime are observed in
March and December and they are minimal in summer. The nighttime seasonal
differences are small; maximum values are observed during the summer months.
As solar activity increases, these regularities remain inchanged.
Knowing the maximum of the vertical electron concentration gradient, it
is possible to predict the maximum frequencies, fmax, of the ionospheric duct
using the extremal parametric method (Shlionskv. 1971, 1978):
J 6370 hn Zh
f = 0.9 • / [Ng + ; — 2- (dN/dh) ] • 10 (l)
max ■*' s 2 max
The global distribution of fmax at equinox for minimum solar activity
(Figure 3) has been obtained from equation (l) and the N(h) profiles. Lati-
tudinal, diurnal, cyclic, and seasonal fmax variations have been calculated
from the empirical model profiles using equation (1). These are given in
Tables 1, 2, and 3. The calculations show that the maximum frequency varia-
tions are determined mainly by the variations of the maximum of the electron
concentration gradient and have the same peculiarities as (Nh')max* The
maximum frequencies exceed considerably the MUF of the F2 layer. Comparing
fmax with MUF for equinox conditions at solar activity minimum along the zero
geomagnetic meridian (Chernyshow and Vasilyeva, 1 976) , we have shown that in
C - 59
10 UhJmax /cm -km
o
15
a)
5
"*-« o "o u ' o*tt»*«
— *-
2 6 . 10 W 18 22
local time
" 10"3(dfr)maxC/OT^m
MO 0 91
K^fUV-km
0 M 8 12 16
local time
10 (dh )maxe/cm3-k
m
20 0 1
0 MO
noon
Figure 2. Results of comparative analyses of (dN/dh)
values calculated from different profiles.
M0 0
midniat
C - 60
Table 1. Diurnal variations of extremal parameters at two solar conditions
ITlinimum solar
activi
tnj Ro,t=75 ,
RiHO , Kp=0-H
Moderate solor conditions.
F-«ffl RiHOO Kp;2-3
From N(h)- prof lies
taoluKliin, Sofco
ionoqrom
eva 1 ^978
From empirical model profiles ne[h)
SohoievQ fflZ .4973 tadukhin, SobblfevQ, W8
LT
\dh /man 9
e/cm5-km Km
e/cnf-km km
10"% f«m
Vi MHz
c/cm4-km Km
e/&mJ-Km tote
00
1,93 228
(5,30)
22,*,
-
-
-
-
-
01
1,50 248
5,30
20,4
2,24
258
6,85 24,6
5,40 328
29,8 38,6
1,56
03
1,50 218
3,00
19,7
2,56
218
2,66 26,2
4,20 308
18,8 33,9
1,29
05
2,30 218
3,10
24,8
1,80
213
3,54 21,9
4,80 288
19,9 36,2
1,65
06
-
-
-
3,40
213
10,9 30,3
8,00 233
27,4 16,5
1,53
07
9,40 188
15,7
50,1
7,60
206
17,8 4.5,2
13,0 243
53,0 59,4
r,3i
08
5,60 188
20,3
41,7
-
-
-
15,0 2**3
63,0 63,8
-
09
9,50 193
24,2
50,5
9,00
198
2?, 8 49, r
13,0 233
56,2 59 ,»
1,21
11
3JJ0*1 193
28,5
&L*
10,0
198
38,7 51,9
13,0 248
70,7 59,5
1,15
13
12,7 195
28,9
58,2
9,0
188
29,8 49,1
12,0 302
84,0 57,5
1,17
15
12,7 198
29,0
56,3
11,6
193
25,0 S5,5
10,0 303
86,2 52.7
0,95
17
11,5 203
21,8
CM, 4
8,6
203
26,6 48,1
11,2 238
50,0 55,1
I,M
18
12,3 203
15,8
57,4
12,5
220
28,0 58,0
21,6 267
68,5 76,6
1,32
19
9,80 203
IM
K.S
7,2
228
21,2 44,1
18,2 253
38,? 70,1
1,59
20
4,30 208
13,7
34,0
-
-
-
13,0 258
26,4 59,3
-
21
3,50 213
11,0
30,8
5,0
228
7,10 36,6
12,4 263
17,8 57,6
1,58
23
2,20 243
4,60
24,5
1,76
238
3,20 21,8
7,6 293
2,58 45,1
2,06
Table 2. Latitude and cycle variations of extremal parameters.
noon
minimum solar activity ^)7=75, Rz"10,Kp"0^1
moderate solar conditions
fio,7 = 175 JkHgg , Kp'2^5
rom N(W) -profiles ionoqram
CoAjKhWj Soboieva tW
tfffffer 5>. %fo te
c i'ir'orn
SobolevQ
Si
empirical model profiles neih)
<972 , M973 r ICQdMKhin.Sokolfe
km
icth-n
9
e/cm-km
Jmai
MHz
"ttP^l
~V ih 'wan L a
fc»g , <978
1
10~MNo
e|cm3.km
Jma,
N\Hz.
16
30
50
faU
89
5,23
21,0
13,7
14,0
T.OO
8,9
3,3
220
258
218
193
193
193
197
3M.3
47,7
<<4.6
25,2
32,0
27,0
16,8
37,6
75,3
60,8
it.1
%,1
18,9
29,5
6,60
20,6
12, <♦
7,60
7,80
3,40
278
263
238
158
193
183
S>,5
77,0
53,1
34,4
32,6
15,1
42,7
75,8
57,9
H5.3
45,8
30, 2,
19,0
20,0
24,0
W,0
J, 00
ro.oo
282
292
292
252
240
213
94,5
145
141
75,0
42, <4
28,9
72,1
71,3
81,2
59,6
49,4
51,2
1,69
0,93
1,40
I, SI
1,10
1,72
midniqhti
0
(10-4)
214
41,2 ST
,9-33,2
11,8
23Z
18,8
56,3
20,1
272
79,3
73,6
1,31
16
H,80
257
16,1
36,1
-
-
-
-
C5,«L
297
100
82,1
-
30
3, MO
212
3,00
30,1
4,20
163
7,93
33,7
23,0
312
50,0
78,9
2,34
50
2,2
24 3
4,60
2*,5
1,98
223
1,58
«.«
7,60
315
21,2
*<5,6
1,98
60
0,6
228
3,20
13,1
-
-
-
-
m
-
-
-
-
69
U-1,8)
223
5,60
23,2
o,9y
248
8,10
16,1
2,70
305
17,2
23,6
1,47
89
2,3
207
6,30
2«»,9
2,80
231
!G,6
27,4
5,0
306
29,8
37,1
1,35
lumbers underlined correspond to high deflection.
C - 61
Figure 3- Isoline of parameters 10" (rrr~)
dh max cm i
. km ( ); fm,x, MHz ( — )
max;
Table 3- Seasonal variation of extremal ionosphere parameters based on
tables of electron density for temperate latitudes.
Activity
Month
3 6 9 12
R2 = ioo
3 6 9 12
-3/dN \ 3
10 \dhimaxe/cm'Ktn 8.40 6,00
h^-Km ^ I98 203
Nj-10 e/cm 24,4 25,8
/max,Mte 47,6 40,2
)° HiL«e/cm-Km 1,50 2,80
hn-Km 265 225
N^e/cm5 6,67 8,33
jtawJMZ 20,2 27,5
noon
7,40 10,0 21,6
208 208 198
21,2 28,2 57,8
44,6 51,8 76,1
midnight
1,54 4,20
9,00 11,7 19,1
222 208 208
51,5 49,4 54,0
49,4 56,2
71,6
1,30
268 275
6,47 5,70
18,8 20,5
288
18,3
33,8
6,00 4,30 3,00
252 273 303
17.2 14,5 9,70
40.3 34,2 28,6
Source: K. Rawer and S. Rama Krishnan (1972)
62
the night hours fmax/MUF = 3 ~:~
k at $ = (16 -
50)
to 6 at $ = 6°N, fmax/MUF = 7
i 8 at $ = (6 -
50)
the daytime.
N. This ratio is equal
and 3-5 at the equator in
USE OF THE F2-LAYER GEOMETRIC PARAMETERS FOR THE
PREDICTION OF THE GRADIENT'S MAXIMUM
Calculating the parameters of the maximum of the vertical gradient from
the analysis of ionograms is a tedious process. Some attempts have been made
to obtain these parameters using the derivatives of an ionogram trace
(Gulyaeva and Shlionsky, 1976). It was shown that the maximum of the gradi-
ent occurs at the plasma frequency, f g , corresponding to the minimum of the
second derivative of an ionogram trace, ( d h'/df ) ml n - However, the other
parameters of this point, namely, the true height, hg, and the maximum value
of the gradient (dN/dh)max cannot be estimated directly from an ionogram.
To determine those, it is suggested to use the maps of the planetary
distribution of the F2-layer parabolic model geometric parameters (Anufrieva
and Shapiro, 1976) widely used for predicting N(h) profiles and h'f curves.
The height of the gradient's maximum is determined by fitting a parabola to
the peak of the F2 layer:
h = h F2 - ymF2 • • 1 - f z/fQzF2 (2)
g m m 9
where hmF2 is the peak height of the F2 layer, ymF2 is the semi th ickness of
the layer, foF2 is the critical frequency, and fg is as defined above. For
the same parabola, the expression of the vertical ionization gradient at the
height, h , is as follows:
(dN/dh) = —Z-r- ^¥Tn ="¥7 (3)
max ymF2 m m 9
where Nm is the peak ionization at the F2 layer, and Ng = 1.2*» x lO^fg2 (f_ is
in MHz and N is in cm-3).
Thus, using the predictions of the F2 crftical frequencies (Chernyshow
and Vasilyeva, 1976); the geometric parameters, hmF2 and ymF2 (Anufrieva and
Shapiro, 1976); the plasma frequency, f g , at the point (dN/dh)max as derived
from the ionograms; and equations (2) and (3), the planetary distribution
of the height, hg , and the gradient maximum value (dN/dh)max may be predicted.
REFERENCES
Anufrieva, T. A., and B. S. Shapiro (1976): Geometric parameters of the F2
layer of the ionosphere. Moscow, Nauka.
Chernishov, 0. V., and T. N. Vasilyeva (1976): Prediction of the maximum
usable frequencies. Moscow, Nauka.
C - 63
Gulyaeva, T. L. , and A. G. Shlionsky (1976): Identification of the maximum
of the vertical ionization gradient from the derivatives of an ionogram
trace. Geomagn. i Aeronomiya, 16:698.
Kadukhin, G. F. , and A. G. Shlionsky (1970): Method to search N(h) profiles
by analogous computer techniques. Geomagn. i Aeronomiya, 10:268.
Kadukhin, G. F., and T. N. Soboleva (1978a): Latitudinal variations of elec-
tron concentration for radio wave propagation. Proceedings of Propaga-
tion of Short Radio Waves, Moscow, IZMIRAN, p. ]~W.
Kadukhin, G. F. , and T. N. Soboleva (1978b): Latitude-temporal variation of
the main parameters of N(h) profiles of a quiet ionosphere. Proceedings
of the Ray Tracing Characteristics of Radio Wave Propagation, Moscow,
Nauka, p. 130.
Rawer, K. , and S. Rama Krishnan (1972): Tentative tables of electron density
for temperate latitudes. Freiburg, FRG.
Soboleva, T. N. (1972): The empirical model of the diurnal distribution of
electron concentration Ne(h) in a geomagnetical ly quiet ionosphere for
temperate latitudes. Preprint no. 20, Moscow, IZMIRAN.
Soboleva, T. N. (1973): A latitude model of electron concentration distribu-
tion in a geomagnetical ly quiet ionosphere. Preprint no. 16, Moscow,
IZMIRAN.
Shlionsky, A. G. (1971): About reflecting MUF of radio waves at the over-
the-earth ionosphere. Preprint no. 12, Moscow, IZMIRAN.
Shlionsky, A, G. (1978): The influence of the main parameters and N(h) pro-
files on the characteristics of radio wave propagation in ionospheric
ducts. Proceedings of Ionospheric Research 26:80.
C - 6k
MODEL CALCULATIONS OF ELECTRIC FIELDS AND CURRENTS IN THE
HIGH-LATITUDE E REGION FOR PREDICTIONS OF IONOSPHERIC VARIATIONS
S. Matsushita and Y. Kamide*
High Altitude Observatory, NCAR
Boulder, Colorado 80307, U.S.A.
Model calculations of ionospheric electric fields and currents in
relation to field-aligned currents are briefly discussed to aid in
predictions (at least for development of prediction techniques) of
ionospheric variations caused by the fields and currents.
1. INTRODUCTION
Electric fields and currents in the high-latitude E region are important
physical parameters for ionospheric variations, because they produce electro-
magnetic drifts and joule heating which cause ionospheric height and density
changes (e.g., Anderson and Matsushita, 1974; Richmond and Matsushita, 1975;
Matsushita, 1976; many references therein). Accordingly, predictions of elec-
tric fields and currents for various geomagnetic conditions may contribute
greatly to ionospheric predictions. In order to attain this goal, model cal-
culations of ionospheric electric fields and currents in relation to field-
aligned currents for both quiet periods and substorms (Kamide and Matsushita,
1979a, b) may deserve a brief introduction here.
By changing ionospheric conductivity distributions as well as field-
aligned current densities and configurations, which depend upon geomagnetic
conditions, various patterns for electric field and current distributions in
the ionosphere have been obtained. In other words, electric fields and cur-
rents can be estimated (or predicted) as soon as the conductivity distributions
and field-aligned currents are either observed directly or assumed from geo-
magnetic conditions. (Conversely, field-aligned currents can roughly be esti-
mated from electric field and current observations with a conductivity model.)
Many diagrams of electric equi-potential distributions and of electric
current vectors in the ionosphere are placed together specially for the present
report to aid in predictions. Some of the diagrams have never been published
before. Two examples of electric field vector distributions are provided to
help the readers in estimating the electric fields from equi-potential diagrams
^Present address: Kyoto Sangyo (Industrial) University, Kamigamo, Kita-Ku,
Kyoto 603, Japan
65
2. CONDUCTIVITY MODELS
For the centered-dipole spherical earth in the equinoctial season, 6 is
colatitude and A is longitude measured eastward from midnight. Height-inte-
grated conductivities are given by Zaa , Z,,, and S0, , where 2ZQQ=ZQ, /sin$ and
^^ v- . ^ tt a . i -i . So . AA ., -UA go ,-OA, , , .
U fl]is ' Here, $ is the inclination angle of a geomagnetic field line
witn respect to the horizontal ionosphere. They are assumed to have the fol-
lowing values and distributions for various models:
1. Simplest Model No conductivity variation with 6 and A (see straight lines
for Model 1 in Figure 1) .
2. Very Quiet Gradually varying conductivity distributions with no local
enhancement (see smooth curves for Model 2 in Figure 1).
3. Quiet Exponentially-distributed enhanced conductivities at (20 <6<30 ,
-90°<A<90°) with a peak at (9=22.5°, A=0°) (see curves for Model 3 in
Figure 1) .
4. Typical Substorm As shown in Figure 2, four auroral regions are as follows
Region I 2O°<0<25° & 0°<A<90° with a peak value of 10 mhos for Sfl,
at (0=22.5°, A=+45.0°)
Region II 20°<6<25° & -90°<A< 0° with a peak value of 40 mhos for EQ,
at (9=22.5°, A=-45.0°) 6A
Region III 25°<6<30° & 0°<A<90° with a peak value of 20 mhos for £0,
at (6=27.5°, A=+45.0°) 9A
Region IV 25°<6<30° & -90°<A< 0° with a peak value of 20 mhos for ZQ,
at (6=27.5°, A=-45.0°). °A
5 . Field-Aligned Current Intensity Variations Same as Model 4 .
6. Field-Aligned Current Location Shifts Same as Model 4.
7 . Conductivity Variations
7.1 Same as Model 4 except Z„,/Zfl„=4.
7.2 Same as Model 4 except Zfl,=0 mho at Region IV.
8 . Additional Field-Aligned Current Same as Model 4 .
The exponentially-distributed enhanced conductivity can be shown by
Za,=Z(max) expf-Ce-e1 ) /DD -(A-Af ) /D, ] , where (0' , A' ) gives the center
location of the enhanced conductivity region at which Z„, is maximum. Ihe
constants Dfi and D, are taken in such a way that £„, becomes approximately
0.2 Z(max) at latitudinal and longitudinal boundaries.
C - 66
300
90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 90
COLATITUDE (degrees)
Fig. 1. Height-integrated conductivity
distributions along the noon-midnight
meridian for Models 1, 2, and 3.
Fig. 2. Schematic diagram to show the
field-aligned currents j i i and auroral
regions I, II, III, and IV with differ-
ent amounts of electric conductivities
FIELD-ALIGNED CURRENT MODELS
As shown in Figure 2, the maximum current density for the poleward-half
(or equatorward-half ) of the exponentially-distributed field-aligned currents
is J
(or j
') at the colatitude
P E P
) (or 9 ) and the longitude X (or
o o o
F P E
X ) with the total downward field-aligned current intensity Iii (or Im ).
o I I I I
Actual numbers of these parameters for the eight main models discussed in
section 2 are shown as follows:
67
1 . Simplest Model
2 . Very Quiet
3. Quiet
3.1 Slight auroral
enhancement
3.2 Double Ii i
4 . Typical Substorm
H A i
o o J
xlO
A/m_
22.5° 90.0° 0.1
P
o
-6
2
5. I
=1
0.2
45.0 2.0
it ii
xlO
A
0.19
0.38
J
xlO
A/m
E
o
-6
2
xlO
A
27. 5V
1.9
-90.0 0.1
-45.0 1.0
" 1.7
0.21
1.1
1.9
6. A Location Shifts
o
6.1 Intense substorm
6.2 Expansive phase
6.3 Recovery phase
7 . E Variations
7A WE96=4
7.2 I0A = 0 at IV
8. Additional I i i
(=4xl05 A) at 6=19.0°
A=-45.0°
67.5
90.0
45.0
2.8
ii
-67.5
1.0
1.6
3.7
ii
-45.0
ii
1.1
1.9
ii
-90.0
ii
2.0
-45.0
1.1
1.9
(morning)
2.3
(evening)
4. RESULTS
The steady-state equations for electric current conservation are solved
numerically for the various models of the electric conductivity and field-
aligned current mentioned in the previous sections (see section 2 in Kamide
and Matsushita, 1979a for the detail). Obtained results of this model calcu-
lation are as follows:
Model
1
2
3.1
3.2
4
5
6.1
6.2
6.3
7.1
7.2
8
Electric Equi-Potential
Distribution
Fig.
3
Fig.
4
Fig.
5
Fig.
6
Fig.
7
Fig.
8
Fig.
9
Fig.
10
Fig.
11
Fig.
12
Fig.
13
Fig.
14
Electric-Field Vector
Distribution
Fig. 15
Fig. 16
Ionospheric Current
Vector Distribution
Fig. 17
Fig. 18
Fig. 19
Fig. 20
Fig. 21
Fig. 22
Fig. 23
Fig. 24
Fig. 25
Fig. 26
Fig. 27
Fig. 28
C - 68
ELECTRIC POTENTIAL
ELECTRIC POTENTIAL
Simple Case
90 -90'
4»= 4 kV
^~~\ <5.
\%.
^""^N^fe. \
Y~-v*. \ \
I I /Jfpl
i ) /^>rO\ I >. 1
\ VY(m§
f^mji) i I
<• — sx /
•e ^^sy 1
Fig. 3
Extremely Quiet
\*0°
4«=3 kV
Fig. 4
ELECTRIC POTENTIAL
ELECTRIC POTENTIAL
•180°
90* -90"
a*. j kv
Quiet Case with SltKht
Auroral Enhancement
Fig. 5
Quiet Casei Double Field-Aligned
Currents
Fig. 6
C - 69
ELECTRIC POTENTIAL
•180*
ELECTRIC POTENTIAL
\-om
Typical Subs torn
90* -90*
&*•* kV
i,P/i„E
Fig. 7
Fig. 8
ELECTRIC POTENTIAL
*180'
ELECTRIC POTENTIAL
tlSO'
90* -90*
Field-Aligned Current Center x=67.5°
Fig. 9
Different Longitudes of Poleward-slde and
Equatorward-slde Field-Aligned Currents
Fig. 10
C - 70
ELECTRIC POTENTIAL
ELECTRIC POTENTIAL
1180'
90* -90*
Different Longitudes of Poleward-slde and
Equatorvard-slde Field-Aligned Currents
Fig. 11
Hall to Pedersen Ratio ~ 4
Fig. 12
ELECTRIC POTENTIAL
1180*
ELECTRIC POTENTIAL
SI 80'
-90*
No Conductivity Enhancement
In Eastward Electro Jet Region
Fig. 13
Downward Field-Aligned Current
ac Poleward Edge of Evening Oval
Fig. 14
C - 71
0=10° rf'*' «'.'.-»
11° *(**■*•&*
16° *" #'«'»'*'«--»
18° «-«-»"«-«-.'.
20° «"* «-•-•'€
U-*44tllUti
ELECTRIC FIELD VECTORS
2b° 4 i i i
ill,
*rn^
^•^ *-»»*♦
;tr«44...i«4444«.*k* •»-fc»?^/. . . . . « •s»s«^,..
3o°«44«4*»*'/ //// i l\v»=^... ... . .k^v*- I
////\\\ '//iv^
32°««4*iiAi/ //// 1 l\ V"*^»-j^. . . . . . ^. v«..
///I\\\
34« • • 4 4 4 4 4 4 4 ///i 1 UVt*jy. . . . . s«v«v.. ,
I
-90°
10 mV/m
Extremely Quiet:
Fig. 15
0-10°
12°
14°
16*
18°
20*
22*
24°
26°
28*
SO*
J2°
J4°
A- -180°
i,P/i,E- i
ELECTRIC FIELD VECTORS
.MM-^UU;^,
. , r ,«*,s\\l 1 ///*•.-
. , . ,>«-#^»\\ I 1 / /*V »■
>Ss\\AJ//*V
^N\W//^v
»^\M/s^
••f'
• k k ■•-•-•^•/» • • •^•-•-••'•'VWlV-. ..
•nr^
kkr^lV
-90*
90°
LONGITUDE
Fig. 16
100 «V/m
I
180*
C - 72
IONOSPHERIC CURRENT VECTORS
;180*
x=o°
Simple Case
50A/km
IONOSPHERIC CURRENT VECTORS
Extremely Quiet
SO A/ka
Fig. 17
Fig. 18
IONOSPHERIC CURRENT VECTORS
x.o*
Met Case with Slight
kuroral Enhancement
90* -90*
200 A/km
IONOSPHERIC CURRENT VECTORS
±180*
100 A/k>
Quiet Casei Double Field-Aligned
Currents
Fig. 19
Fig. 20
C - 73
IONOSPHERIC CURRENT VECTORS
IONOSPHERIC CURRENT VECTORS
x.o*
Typical Substorm
90* -»0*
2 */■
±l»0'
I,P/I,E ■ 1
Fig. 21
Fig. 22
IONOSPHERIC CURRENT VECTORS
IONOSPHERIC CURRENT VECTORS
±180*
W -tO'KrrmTT
Field-Aligned Current Center >"67.5°
Fig- 23
Different Longitudes of Poleward -side and
Equatorw«rd-»lde Field-Aligned Currents
Fig. 24
C - Ik
IONOSPHERIC CURRENT VECTORS
IONOSPHERIC CURRENT VECTORS
M80*
90* -90'
1180*
2 Va
Different Longitudes of Poleward-side and
Equatorward-slde Field-Aligned Currents
Fig. 25
Hall to Pedersen Ratio — 4
Fig. 26
IONOSPHERIC CURRENT VECTORS
IONOSPHERIC CURRENT VECTORS
±i«o*
90* -90'
x-o*
2 A/»
No Conductivity Enhancement
In Eastward Electro jet Regie
Fig. 27
Downward Field -Aligned Current
at Poleward Edge of Evening Oval
Fig. 28
C - 75
5. CONCLUSION
Since computed results are in satisfactory agreement with observations,
those diagrams shown for different geomagnetic conditions may aid in predic-
tions. Studies of time sequences of the electric potential and current-vector
distributions in the form of movies are under preparation.
We are grateful to Drs. T. Holzer, A. D. Richmond, and R. G. Roble for
their helpful discussions and to Dr. J. C. Adams for his able assistance in
computer programming during an early phase of the present study. The National
Center for Atmospheric Research is sponsored by the National Science Foundation,
REFERENCES
Anderson, D. N. , and S. Matsushita (1974): Seasonal differences in the low-
latitude F2-region ionization density caused by ExB drift and neutral
wind. J. Atmos. Terr. Phys . , 36:2001.
Kamide, Y. , and S. Matsushita (1979a): Simulation studies of ionospheric
electric fields and currents in relation to field-aligned currents,
1. Quiet periods. J. Geophys . Res. , submitted.
Kamide, Y. , and S. Matsushita (1979b): Simulation studies of ionospheric
electric fields and currents in relation to field-aligned currents,
2. Substorms. J. Geophys. Res . , submitted.
Matsushita, S. (1976): Ionospheric and thermospheric responses during August
1972 storms - A review. Space Sci. Rev. , 19:713.
Richmond, A. D. , and S. Matsushita (1975): Thermospheric response to a magnetic
substorm. J. Geophys . Res ♦ , 80:2839.
76
STATISTICAL PREDICTION OF ES-LAYER PARAMETERS AND
ECHO-SIGNAL CHARACTERISTICS
T. S. Kerblay, G. N. Nosova
nstitute of Terrestrial Magnetism, Ionosphere and Radio Wave
Propagation of the Academy of Sciences of the USSR
Moscow Region, USSR
To calculate and predict Es echo-signal characteristics, an
analytical expression describing the spatial structure of the E_-
layer is suggested. On the basis of published experimental
results, statistical estimations of the model parameters have been
obta ined.
An empi r ical -stati stical basis is expedient to use at present when making
predictions of the Es-layer since an unambiguous relationship between the
solar emission, the aeronomical and other characteristics of the ionospheric
E-layer, and the parameters of the Es~layer has not been established. Fur-
ther, the significant variability of the Es~layer parameters makes it
necessary to apply the statistical method in their description.
To make predictions for the Es~layer, therefore, a model should be
selected that can satisfactorily describe the spatial structure of the layer
and the empirical and statistical variations in the model parameters. It
should be noted that the number of parameters that may characterize the
ionization intensity in the Es~layer and its spatial distribution is much
higher than the number of parameters for the regular layers.
The following expression has been adopted (Kerblay and Nosova, 1976) to
use when simulating the large-scale structure (t of about the order of 100 km)
of the Es-layer to calculate the characteristics of signal reflected from
that layer:
N = N
o
kekZ
(l+e^V
Ksi
/2ttX . \ /2ttY . . \
(0
where X, Y, and Z are the Cartesian coordinates with the origin at the
maximum of the layer; NQ is the mean electron number density in the layer
maximum which may be estimated by fbE , NQ = A(fbEs)2; K is the value
characterizing the amplitude of plasma frequency fluctuations in a horizontal
plane; tx and t2 are the scales of i nhomogenei ty along the X and Y axes,
respectively; $ and \p are the phase shifts determining the position of the
periodic structure relative to the coordinate origin.
77
The distribution of the electron number density in the layer as a func-
tion of altitude is represented by the model of thin layer (the Epstein
layer). The advantage of the model is that it provides an analytical
solution for the reflection coefficient that may be used to estimate the
energy characteristics of a signal reflected from the layer.
The hal f- thi ckness of such a layer, £, is related to the parameter
h by £ = 0.56 TT/fi.
Thus, the prediction of the Es-layer includes the prediction of the
parameters contained in expression (1), namely N H , t2 , k, K, (f), and \p .
The statistical estimates of these parameters have been obtained by analyzing
the published experimental results on the basis of the methods of vertical
sounding, backscatter ing, incoherent scattering, etc. The distribution laws
were determined, and the most probable values and variances were estimated
for the various parameters.
The value N is estimated by using one of the probability-statistic
methods for determining the frequency parameters of the Es-layer (fQEs and
f|DEs) (Kerblay, 1964; Mikhailova and Ovezgeldyev, 1976; Minullin and
Eliseeva, 1976). Such methods make it possible to determine the diurnal,
seasonal, and global variations in the occurrence probabilities of fQEs and
ft-,Es above a set value. Since clear variations of fQEs and fbEs with the
solar cycle have not been found, the calculation methods give the values
averaged over the solar cycle. According to modern concepts, the maximum
electron number density in the Es~layer is determined through f ^Es .
We shall refrain from dwelling on the well-known diurnal, seasonal, and
global variations of fbEs. The parameter characterizing the layer thickness £
has been obtained mainly from the published results of rocket measurements.
Figure 1 shows the histogram of the £ distribution for 93 observations. It
follows from the figure that the most probable value of £ i s of the order of
1 km, and E, = 1.2 km.
The time variations in f^Eg at ver-
tical soundings permit the value of K to
be estimated by assuming that the time
variations are relevant to the passage of
a series of i nhomogenei t ies over the
measurement point at a velocity V =
80-100 m s-1.
The value of K was determined by
using the simultaneous measurements of
Es from 1972, when more frequent vertical
soundings with 10- and 15-min observa-
tions of the Es-layer were carried out at
the European network of stations. (The
analysis was made using the data from
the stations listed in Table 1.)
60
50
£40]-
\50
c*=a 20
E
S 10
5 6 S,Km
c - 78
Figure 1. Distribution of semi
thickness of layer Es.
Table 1. Measurement stations by location
Stat ion
T
X
0
Moscow
55.5
37.9
50.8
Rugen
54.6
13.6
54.5
De B i 1 1
52.1
5.2
54.0
Slough
51-5
0.6
54.3
Dourbes
50.6
4.6
56.3
Kiev
50.5
30.5
47-5
Pruhonice
50.5
14.5
60.4
Frei burg
48.1
7.8
48.4
Rostov- Don
47-0
41.5
42.5
Garchi
47.3
3.1
49.6
Graz
47.1
15.5
47-0
Bekescsaba
46.7
21 .2
46.0
Note: (J) - geomagnetic latitude
Y - geographic latitude
X - geographic longitude
Figure 2 shows the histogram based on observations of fbEs from the
middle-latitude ionospheric stations listed in_Table 1. The histogram pre-
sents the most probable value of K = 0.25 and K = 0.3-
The
It should
tudinal ) ,
expressio
exper imen
y
to
30r
20
10
scales of inhomogeneous structure t1 and t can also be characterized.
first be noted that the two scales, t (lateral) and t (longi-
of the structure have been inserted to increase the generality of
n (1). It is impossible to obtain the two scales from the available
tal results or theoretical works because of the absence of a
unified opinion about the degree of
anisotropy of the large-scale structure
of Es and about the orientation of the
inhomogenei t ies . It is necessary,
therefore, to characterize only_the
mean value t = 1/2 (I + l2) . I is
determined from several sources,
including radar measurements, back-
scattering, incoherent scattering,
vertical sounding, etc. The data from
the various sources are in a_ satis-
factory agreement and give t ranging
from 100 km to 1000 km, with the most
probable values in the 100-300 km
region. _Figure 3 presents the histo-
gram of £ obtained from the data of
vertical sounding. The periods_with
increased f^Eg were scaled to t on the
assumption that they are the effect of
passage of the Es i nhomogenei ty over
J I
0 0,2 QA 0,6 0,8 i,0 K
Figure 2. Distribution of param-
eter K.
-l
the station at a velocity of 100 m s
Similar values of I have been obtained
by comparing the moments of
79
7
/o
60
50-
40.
30-
20
10
o m 360 540 720 goo i,m
Figure 3. Distribution
of horizontal size of
simultaneous observations of Es in vertical and
inclined soundings (Kerblay et al., 1978a).
When the radio wave propagation characteristics
are calculated, the values of $ and i|; are
determined as functions of the position of the
Es-layer inhomogenei ty center relative to the
region of radio signal reflection. The method
for calculating the trajectory characteristics
of the signal reflected from the Es-layer is
based on the above described model using the
mathematical formalism developed at the
laboratory for calculating the ray trajectories
in three-dimens ional ly inhomogeneous medium
(see the reports of Kerblay et al., 1978b).
The method developed as appl ied to the
Es-layer permits the distance D, elevations
Ax and A2 and azimuth deviation to be calcu-
lated at the parameters of the layer model set
statistically or determined experimentally in
vertical soundings.
Calculation results were compared with
the values measured along the lines of inclined sounding on the basis of pub-
lished data (Miya and Sasaki, 1966) and using the experimental results
obtained along the Arkhangelsk-Kazan path. Despite the statistical setting
of the majority of model parameters, a satisfactory agreement has been
obtained between the calculated results and experimental data, which indicates
the developed method may be used to estimate the characteristics of a signal
reflected from the Es-layer.
REFERENCES
Kerblay, T. S., and G. N. Nosova (1976): About the model of the large-scale
spatial structure of the middle-latitude sporadic E. In: The Physics and
Empirical Simulation of the Ionosphere, Nauka, Moscow, 104.
Kerblay, T. S. (1964): Instruction Manual: Calculations of the Short Wave
Radio Communication Frequencies Reflected from the Es~layer. Nauka,
Moscow.
Kerblay, T. S., R. A. Kurganov, R. G. Minullin, and G. N. Nosova (1978a):
Horizontal sizes and velocities of the E -clouds by experiment carried
out on the radio paths Salekhard-Tumen. Ionospheric Research, 26:64.
Kerblay, T. S., G. N. Nosova, R. G. Minullin, R. A. Kurganov, A. M. Nasirov,
and N. V. Leshenko (1978b): Experimental investigations of Es-signals
for radio paths about 1000 km long. International Symposium on Radio
Waves and Ionosphere, URSI, Helsinki, Finland, August 21.
Mikhailova, G. V., and 0. 0. Ovezgeldyev (1976): An empirical model of the
middle-latitude sporadic E. I zv . Akad. Nauk Turkm. SSR, ser. fiz-thehn.,
Khim, geol . , 3:65-
80
Minullin, R. G., and T. Ya . Eliseeva (1976): Regularities of integral
distributions of the top frequencies of the sporadic E. Geomagn. i
Aeron. , 16(4) : 726.
Miya, K. , and T. Sasaki (1966): Characteristics of ionospheric E^ propaga-
tion and calculation of E_ signal strength. Radio Science 1(1) :99-
81
FORECAST OF CRITICAL FREQUENCY AND HEIGHT OF
MAXIMUM DENSITY OF THE MID-LATITUDE E-LAYER
I vanov-Kholodny G.S. and Nusinov A. A.
Institute of Applied Geophysics, Goscomhydromet
Moscow
USSR
The scheme of forecasting of E-layer critical frequency, height of
maximum and scale height is proposed. The scheme is based on main
physical processes responsible for the layer formation and includes
Solar ultraviolet and X-ray emission fluxes as initial parameters.
The methods of forecasting the E-layer parameters are based at present
on some empirical relations obtained as a result of statistical data pro-
cessing of the vertical ionospheric sounding (see e.g., Ching and Chiu,
1968; Tchernishov and Vasilieva, 1975). The initial parameters for calcula-
tion of critical frequencies are as a rule the sunspot number and the solar
zenith angle. Such methods of forecasting give some average ionospheric
parameters, but they neither account for specific hel io-geophysical condi-
tions, nor reflect the connections between these parameters and causes of
their variations. For computation of radio wave propagation at middle
distances, it is necessary to know the main E-layer parameters, i.e. critical
frequency, the height of maximum and effective thickness. These parameters
are determined mainly by Solar ultraviolet and X-ray fluxes varying
significantly from day to day. Though the solar activity indices mainly
used for ionospheric forecasts (the sunspot number and radio flux at 10,7 cm)
give the average levels of fluxes, they do not reflect short-time variations
of their values. So approximate mean ionospheric parameter values calculated
by means of present methods appear to be insufficiently accurate and can be
used only for mean value evaluations.
A forecast where physical processes in the ionosphere are taken into
account does not have such drawbacks. For day-time mid-latitude E-layer the
processes determining layer's parameters are photoionizat ion and complex of
charge-exchange reactions and recombination. Ionization rate is determined
by Sun ultraviolet and X-ray emission, as well as neutral atmosphere parame-
ters. The development of satellite means of observations allows to obtain
regularly emission flux data even now. However, accurate data on neutral
atmosphere variations at E-layer heights have not been obtained yet. Thus
the problem of the comprehensive calculation of E-layer parameters cannot be
solved at present. Therefore, in order to predict the E-layer parameters,
we have to use the forecast consisting of both determinated part based on
C - 82
the knowledge of physical processes resulting in layer formation and part
based on statistical processing.
Ionization rate computations for E-layer using spect
Kholodny and Firsov (197^) and atmosphere model (Jacchia,
the main part of E-layer ionization is caused by the Sun
Ly 3 (1026 A) and CIII (977 A) lines. This conclusion is
tical analysis of E-layer critical frequency behavior bot
( I vanov-Kholodny and Nusinov, 1976) and during the time o
on the Sun ( I vanov-Kholodny et al., 1976). In order to r
variations, it is useful to introduce a structure paramet
ratio of ionization rate by X-ray (30-100 A) radiation to
radiation at the E-layer maximum height: R =q /q under a
u X u
Sun activity, when ultraviolet and X-ray emission fluxes
rum of Ivanov-
1970 show that
radiation in the
confirmed by statis-
h during the year
f some X-ray bursts
eveal E-layer main
er R . 1 1 i s a
that of ul traviol et
certain state of
are equal to U
and X correspondingly, and ionization rate in the layer maximum is q
ionization rate q under arbitrary solar activity is as follows:
Then
q =
( R(
V— a.
l+R
1+R.
(1)
where X and U - the radiation fluxes in the period to be forecasted.
The study of ionosphere behaviour at the moments of X-ray bursts (Ivanov-
Kholodny et al., 1977) have shown that R value monotonously varied for a
year period from R = 0.16 in wintertime to 0.22 in equinoxes and 0.32 in
summer. Ionization rate computations demonstrate that such variation is
caused by changing atmosphere structure at the turbopause level. This chang-
ing is connected with a sharp decrease of molecular oxygen effective height
scale in wintertime. Simultaneously this changing causes some other effects
inherent in E-layer seasonal variations. As it is known critical frequency
f E varies with zenith angle z as cosPz at daytime, where the power p ^ 1.07
in summer and p % 1.23 in winter (see e.g. I vanov-Kholodny and Nusinov,
1977)- Variations of p-values have also been obtained as a result of ioniza-
tion rate computations ( I vanov-Kholodny and Nusinov, 1977) providing for
atmosphere seasonal variations at the turbopause level. The same computations
give also the value of winter anomaly (Appleton, 1963), which coincides with
the observed one: the qQ value extrapolated to the same zenith angle de-
creases as much as 12 per cent from winter to summertime. Thus E-layer
critical frequency at an arbitrary moment can be found in accordance with (1)
from equation:
(f
E)k = I cosPz
(P,
1+R.
1+R.
(2)
where the phase factor depending on the day number D can be introduced to
account for seasonal changes of p, R and I values:
§(D) = sin [__2tt_ (D-80)]
365
(3)
C - 83
Then these values are the following:
R = 0.23 + 0.07 $ (D) (4a)
o
p = 1.15- 0.08 $ (D) (4b)
I = I„[ 1-0.06 $ (D)] (4c)
I. depends on the absolute values of radiation fluxes, ionizing the
o J
atmosphere at the heights of 100:120 km, as well as on a number of atmos-
pheric parameters. Uncertainties in determination of these values do not
permit to calculate I immediately. Therefore I can be found by means of
statistical analysis of ionospheric data, where equation (2) is used as a
regression equation. Estimation based on Moscow station data gives
I = 190 MHz1*. From the processing of data obtained in other stations the
value might be made more precise. Just equations (2-4) give formulae to
forecast E-layer critical frequency.
It is well known that f E decreases by the value about 0.1 MHz under
strong magnetic disturbances (Beynon and Brown, 1959; Appleton and Lyon,
1961). Analysis made in I vanov-Khol odny and Nusinov (1977b) showed that
these f E variations could be due to both change of atmosphere composition
(the increase of nitric oxyde concentration, advected from polar regions)
and considerable increase of its density. Data available now are not
sufficient to calculate these phenomena. Therefore to forecast the effect
caused by magnetic disturbances it is possible to use the results of
statistical analysis made in I vanov-Kholodny and Nusinov (1977b). In
accordance with I vanov-Kholodny and Nusinov (1977b), to evaluate the effect
of geomagnetic disturbance with a given Ap-index, it is necessary to subtract
value 0,4 Ap from equation (2), with Ap-index being taken for previous day.
Formula (2) includes only relative values of radiation fluxes, so the
forecast does not need a precise calibration of detectors installed onboard
the satellite observatory. According to Schmidtke et al . (1977) fluxes in
lines 1026 A and 977 A causing ionization in E-layer and a flux in line
304 A vary identically. Therefore the 304 A line for which we have the most
reliable data may be used to forecast the critical frequency. Moreover,
instead of X-ray flux within the range of 30-100 A, which cannot be easily
measured, now it is possible to use 8-20 A flux data. Measurements of such
a flux are more reliable and do not require complicated instruments. It was
shown in I vanov-Kholodny et al. (1976) that the ratio X/X in (2) ought to
_ () o
be replaced by square root relative intensity within 8-20 A range.
For accurate calculation of radio transmission frequencies, it is neces-
sary to know not only the critical frequency of the layer, but also its
main geometric parameters, i.e. height of maximum h and scale height H. So
far these values either have not been used in forecasts at all, or have been
considered to be constant (for example in Ching and Chiu (1968) h= 1 1 0 km and
H=10 km). Analysis of ionospheric observations (see e.g. Robinson, 1959)
shows that the simple Chapman's equation
h=hQ - H In cos Z (5)
C - 84
can be used to forecast the height of maximum. However, both the results of
observations (Robinson, I960; Butcher, 1970; Whitehead, 1973) and computa-
tions ( I vanov-Kholondy and Nusinov, 1977a) prove, that h and H values are
changed with seasons: from summer to winter h value changes from ^ 107 km to
"ii 103 km and H value - from 6:9 km in summer to ?>:k km in winter. Using
seasonal factor (3) it is possible to write approximate formulae for h and
H for different seasons:
hQ = 105 + 2 • $ (D) (6a)
H = 5£ + 2 • $ (D) (6b)
These expressions agree with both observations and computations. Their ac-
curacy is about 1:1.5 km, and it is sufficient for calculations of M2000-
coefficient with relative error of 2:3 percent.
Thus a forecast of critical frequency and geometric parameters of E-
layer can be given due to simple calculations according to (2-6). Initial
data for such forecast are values characterizing conditions of E-layer forma-
tion for a certain day, i.e. fluxes of ionizing radiation and magnetic
activity indices. Hence it is sufficient to know only relative values of the
fluxes. A number of values in such as p, I and R describes seasonal varia-
tions of atmosphere structure. The average values of p, I and R may be
obtained by statistical data processing and their annual variations - by
model computations.
The scheme of forecast under consideration is intermediate between
exact computation and statistical model. This method has some advantages as
compared with existing ones. Above all it allows to forecast (or to
calculate through the data available) the state of ionosphere for a concrete
moment, characterized by a given set of hel io-geophys ical parameters. Further
it includes only the values immediately determining the E-layer formation and
dynamics. It should be noted that the existing schemes of forecasting give
only the monthly mean f E value depending on average sunspot number. The
method also allows to forecast variations of E-layer critical frequency
during geomagnetic disturbances. Moreover, this forecasting scheme gives an
opportunity to calculate seasonal variations as well as short-time variations
caused by rapid changes of solar radiation flux (bursts). In many cases
there are no visible changes on the Sun's surface during these rapid varia-
tions, so they do not take place in the existing schemes of forecasting.
REFERENCES
Appleton, E. (1963): J. Atmos. Terr. Phys. , 25=577-
Appleton, E. V., and A. J. Lyon (1961): J. Atmos. Terr. Phys., 21:73.
Beynon, W. Y. G., and G. M. Brown (1959): J. Atmos. Terr. Phys. , 14:138
Butcher, E. (1970): J. Atmos. Terr. Phys., 32:97-
C - 85
Ching, B. K. , and Y. T. Chiu (1968): J. Atmos . Terr. Phys., 35:1615-
I vanov-Kholodny, G. S., and V. V. Firsov (197*0: Geomagn. i aeronomy,
14:188.
I vanov-Kholodny , G. S., and A. A. Nusinov (1976): Geomagn. i aeronomy,
16:76.
I vanov-Kholodny , G. S., L. H. Lestchenko, and I. N. Odintsova (1976):
Geomagn. i aeronomy, 16:246.
I vanov-Kholodny, G. S., L. N. Lestchenko, A. A. Nusinov, and I. N. Odintsova
(1977): Geomagn. i aeronomy, 17:839-
I vanov-Kholodny, G. S., and A. A. Nusinov (1977a): Geomagn. i aeronomy,
17:1018.
I vanov-Kholodny , G. S., and A. A. Nusinov (1977b): Geomagn. i aeronomy,
17:423.
Jacchia, L. G. (1971): Spec. Rept. No. 332. Smithsonian Inst. Astrophys.
Observ., Cambridge, Mass.
Robinson, B. J. (1959): Reports on Progress in Physics, 22:241.
Robinson, B. J. (I960): J. Atmos. Terr. Phys., 18:215-
Schmidtke, G., K. Rawer, H. Botzek, D. Norbert, and K. Holzer (1977):
J. Geophys. Res., 82:2423.
Tchernishov, 0. V., and T. N. Vasilieva (1975): "The forecast of MUF".
"Nauka", Moscow.
Whitehead, J. D. (1973): J. Atmos. Terr. Phys., 35:183.
C - 86
DAYTIME SPORADIC-E BLANKETING FREQUENCY PREDICTION
A. E. Giraldez
LIARA, Avda. Libertador 327
Vicente Lopez, Buenos Aires, Argentina
A prediction method for the daytime median hourly values of the Sporadic-E
layer blanketing frequency (fbEsj in particular for the South American sector,
is presented. The fbEs values show dependence on Wolf number (R), solar zenith
angle (X) and geographic latitude {%) . This method calculates the frequency
value (fbEs) for midlatitudes provided that R, local time, geographic latitude
and month number are given as input conditions.
Comparisons with scaled data from ionosondes between 20 and 55 latitude, for
an R excursion from 10 up to 200 are shown. This prediction method provides
daytime fbEs values within 10$ error for the South American sector. Northern
hemisphere, Africa and Australia also show good agreement, within 10$ error ex-
cept for latitudes higher than 40° in Winter time.
1.- INTRODUCTION
Sporadic-E layers, due to their special characteristics, permit a narrow margin of predic-
tion, but only during quiet time conditions.
The formation mechanism at midlatitudes seems to be the wind- shear mechanism (Whitehead,
I960, 1961, 1962 ; Axford, l96l, 1963; Hall, 1964; Hines, 1964; Chimonas and Axford, 1968),
assumption which is supported by experimental findings (Rosenberg and Edwards, 1964;
Bowen et al , 1964; Rosenberg et al , 1964; MacLeod, 1966; Wright, 1967; Wright et al , 1967;
Wright and Pedor, 1969; Miller and Smith, 1975; Harper et al , 1975).
The fact that Es layers are formed by metallic ions has been widely established by mass-
spectrometer measurements between 90 and 130 km (Istomin, 1963; Narcisi and Bailey, 1965;
Narcisi, 1968, 1973; Young et al , 1967; Anderson and Barth, 1971; Johanessen and Krann-
kowsky, 1972; Zbinden et al , 1975; Goldberg, 1975) and recently also using backscatter by
Behnke and Vickrey, 1975.
Processes which produce the ionization of metal ions necessary to form Es layers have been
investigated in detail (Swlder, 1969; Ferguson, 1972; Brown, 1973; Baggaley and Cummack,
1974; Poole and Nicholson, 1975) > and the diurnal variation of metal-ions is mainly deter-
mined by the concentrations of 02 and NO (Miller and Smith, 1976). Based on the above
mentioned assumptions about the mechanism of formation and the source of the metal-ions,
the next point to be considered is the opportunity of formation of an Es layer. Taking
into account that wind-shear theory requires a horizontal shear of neutral winds, gravity
waves and tidal winds are the most appropriate phenomena to give rise to a Es layer. As
the magnitudes of tides and gravity waves are comparable, (Hines, 1963) the persistence
of the tidal winds and the random nature of the gravity wave spectrum indicates that long-
term features of Sporadlc-E layers should be dominated by the tidal modes (Smith and Mil-
C - 87
Her, 1977). The observation of Es layers by means of ionosondes, provides information
about virtual height (h'Es), and two maximum frequencies, namely fbEs, foEs.
This paper deals only with fbEs, which is the nearest Es critical frequency to the mean
plasma density of the layer. (Rawer, 1962; Reddy and Rao, 1968; Whitehead, 1972), and t^«re-
fore the least influenced by short duration wind variability, as is the case of foEs.
Due to the arguments expressed, three main variables must be taken into account if a pre-
diction of fbEs is attempted. Solar zenith angle, which governs 0* and N$ concentrations
and R (Wolf) number, or any other solar activity index which proves to be related to signi-
ficant E region ion concentration. A third variable to take into account is geographic la-
titude, due to Es dependence on tides, because the current knowledge on solar tides (Voll-
and and Mayr, 197^. 1972, 1977; Volland and Grellman, 1977; Richmond, 1971, 1977; Richmond
et al, 1976; Evans, 1976; Lindzen, 197'+;) would indicate that at E region heights, ~-midiur-
nal tideswlth a strong latitudinal variability are important. Also magnetic field vector is
fundamental, according to wind shear theory (Reddy & Matsushita , 1968; 1969), and geomagne-
tic coordinates necessary. In this case geographic coordinates are b>i'ng used, for simpli-
city, and assumed that geographical coordinates also take account the wind shear parameters
at least aproximately. The prediction method developed in this paper shows that the daytime
dependence of fbEs with the R value is roughly the same as the one obtained by Bosolasco
and Elena (1963) and Heisler and Whitehead (1964) for foEs. Also the mean value of fbEs had
a diurnal variation similar in phase and amplitude to foE, a result coneistent with the
idea that the Es is due to a redistribution of existing ionization. The practical applica-
tions of this method are related with HF radio propagation predictions. HF links predicted
through the use of the P layer ionization might be seriously disturbed by Es ionization up
to 2000 km distance from the transmitter, as Es layers can act as a low altitude reflecting
layer which renders the MUF F2 factor meaningless. As percent of time with presence of Es
layers at midlatitudes is, during daytime higher than 30% of time (CCIR 1976), an estima-
tion of maximum fp^'^uency reflected by Es layers is a necessary tool to be taken into
account as a perturbation factor in HF propagation predictions. (CCIR, Doc. 6/I77 (I976);
CCIR, Study Program 4A-2/6).
2.- PREDICTION TECHNIQUE
2.1.- STATIONS INFORMATION
Hourly mean values of fbEs scaled at four South American stations located between 23.5° S
and 51.7° S geographic latitude and with a small longitudinal dispersion are used. The pe-
riod of analysis covers from 1957 UP to 197^. Detailed station information is provided in
table 1.
TABLE 1
Station name
Geographic
long. latit,
Geomagnetic
long. latit.
Sao Paulo
313. k
-23.6
Tucuma"n
29^.6
-26.9
Buenos Aires
301.2
-34.6
Port Stanley
302.2
-51.7
21.09
3.33
9.4
9.09
-12.8
-15.4
-23.2
-40.4
88
2.2.- Data handling
The data are arranged by geographic latitude, R number and cos (X) values rather than hour,
season and year.
Data corresponding to months with severe geomagnetic perturbations (Ap> 50) covering more
than half the month are not considered.
There have been made a two dimensional array In R and cos (X) values for each station under
study. Each line goes from cos (X) = 0 up to cos (X) = 1. Each cell In the line Includes
data within & cos(X) = 0.1. Each column goes from R = 10 up to R = 200, and each cell In
the column Includes data within A R = 20.
Thus, a 10x10 array of data Is obtained for each station.
A mean value In each cell Is calculated, together with the corresponding standard deviation
of data tra the cell. It Is remarcable to point out that In each cell the dispersion from
the mean does not rise over 10$, and in most cases lays below 5%, as shown in Figure 1.
0.2
^0.1
1 fr1 k ** ¥ # 4 fe $
- - - * * * * * - r
0 1 .2 .3 .4 .5 .6 .7 .8 9 10
COS *
Pig. 1. Average standard deviation (0~) over the mean value fbEs for
the four stations under analysis, against cos X. Bars indicate disper-
sion limits. • , R • 50; A , R = 100; O , R = 150; X R = 200.
2«3.- Analysis of data
There have been assumed a functional dependence of fbEs on R and cos (X) such as:
fbEs(R.X) = F(R).(cos(X))n (l)
2.3.1.- Solar zenith angle dependence
For constant R values in the two dimmensional array made for each station mentioned before,
an exponential curve fitting by the least squares method is performed for each R interval
value and each station for the function:
fbEs = a. (cos X)b
(2)
with the following results:
The exponent is almost constant during all the excursion over R values for each station,
but grows with latitude, as shown in Figure 2.
The correlation coefficient in the exponential curve fit results r> O.967 for cells bet-
ween 0.1 £ cos X <C 1. in every case.
09
' I I I I I I I
• I I ■ I I
0.40
0.35
0.30
0.25
a2o
51.70
34.90
I
-i 1 1 1
40
60
120
i i i
160
20
30 40
50
LATITUDE
Pig. 2. Left figure shows b against R for the four latitudes. The
numbers on each curve are the corresponding South latitude of the
station. The figure on the right shows b against South latitude.
Dots are mean values, bars are standard deviation.
In order to avoid a latitudinal dependent exponent in the (cos X)b expression, it will be
adopted a constant b value, and the latitudinal dependence will be treated as a different
term. The exponent adopted is b * 0,25 as for the Normal E layer (K. Davies, 1965), to
permit further comparison between normal E and Sporadic-E frequency expressions.
2.3.2.- R (Wolf number) dependence
The analysis of data to find out the functional dependence of fbEs upon R follows similar
lines as those of paragraph 2.3.1.
Linear, logaritmic and exponential curve fitting is performed for each cos X value along
the columns of the array. Results show that exponential curve fitting have a poor correla-
tion, but linear and logaritmic fitting presents similarly good correlation coefficients
(r > 0.9).
log. curve fit : a
linear curve fit: a
+ b.log(R)
+ b.R
= F(R)
= F(R)
(3)
(4)
The election between log and linear function is then made through the analysis of their in-
dependence on cos X.
The comparison of (b/a) coefficients as a function of cos X for both curves, as shown in
Figure 3, indicates that linear regression is almost independent on X value, while log is
not. Thus, linear dependence of frequency on R values is adopted, with a functional depen-
90
dence:
fbEs (R)
1 + 1.737^xlO~3 .R
(5)
xio3 15
a
as
C
linear courvefit : _fe\ = 1
V V me
73778 xW? 31- 0.027
-5
4.7x10
04
06
06
' log courvefit /b\
^a Jmitn
s 0.002
:0.0»
= 01100
02
04
OS
08 1
COS "X
Pig. 3.- Top figure
shows experimental values
(dots) as well as disper-
sion (CT) and relative
error G~/(b/a) for the
linear curve fit as func-
tion of 6«s X values.
Bottom figure shows the
same data i.sr log curve
fit.
2.3.3.- Latitudinal dependence
As It is observed in fig. 2, there is a strong latitudinal influence upon the critical
layer frequency. This section is devoted to find out the third term of the equation, which
relates cos X and latitude.
The analysis of the equation,
fbEs(observed)/(cos X". P(R)) = F(X,fc)
(6)
where 7* = geographic latitude
for each cell of the 10x10 array, results in a group of values for F(X^ ) as function of
latitude and X angle values, after evaluating the mean value of each column. (R values)
Those values obtained are shown in fig. 4 (crosses).
Intermediate points on fig. k are obtained by Lagrange interpolation method. This procedu-
re visualizes the corresponding latitude of the maximum F(X,^) function for each value of
cos X. As is observed in the same figure, F(X,^ ) is a single maximum function for each
cos X value, with a different maximum position for each one.
Figure 5 shows those maximum from Fig. 4, as a function of cos X, together with the empiri-
cal function which fits the curve.
This is not the most appropriate place to analyze the physical meaning of Fig. 5» but any-
way, it means that independently of the solar activity and the charge exchange mechanism
efficiency, there is a semidiurnal symetric effect which drives maximum wind-shear mecha-
nism efficiency towards the pole and after towards the equator in the morning, and which
repeats in the afternoon. This effect requires a deeper analysis to be adequately explain-
C - 91
H.H
| H 0
x
s
3.S
3.0
9= CD5 :x
1 3 ' S ' 32'^ '■* ' 4 ' Hb ' 6 'a!
LHTITUDE
Pig. 4.- Figure 4- shows
formula (6 ) above as a
function of latitude ,
with cos X as a parameter
Crosses indicate experi-
mental values. The conti-
nuous line results from
Lagrange interpolation.
.9
" ""■"^-,5>-«^
.7
X XQ.
X h
.5
X </
V
empirical courve Nx ■'
.3
.1
, 0 -■--■"""" — experimental data
2D*
30*
40*
QEOQRAPHC LATITUDE
50*
Fig. 5." Maximum values of Fig. 4 for each cos X value (crosses) and
empirical curve (cicles) as a function of geographic latitude.
ed, but as pointed out in the introduction, this effect is related to E region tidal wind
system.
The expression obtained to fit Fig. 5 data is:
$= lat(max.F(X.*)) = 150°(cos X-cos^Xf coS3X/9) +7'
(7)
C - 92
F(X, A ) is reasonably good fitted by a function of the form;
P(^,> I = A(XJ . exp( - (jM -$)2/S(X)
(81
with:
A(X.' = maximum value of F(X. ,Al
All data on expression (8) are known, except S(X).
The solution of equation (8) for S(X) as function of latitude and cos X values gives a set
of values shown in Pig. 6 (crosses). Curve fitting for those values (full line) is shown in
the same figure.
xlO-
IH.
II.
I
w S.
S [ X ) = 2525. COBS X f '
I « I » I ■ » I 4 «
1.2
i.h IE ■ a
<D5 X
Pig. 6.- Values of
S(cos X) as function of
cos X values correspond-
ing to equation (8)
(crosses), and the least
squares curve fit (full
line) with the corres-
ponding equation of the
curve.
with:
S(X) = 2525 . (cos X)"*?3
(9)
Thus, the latitudinal term is:
F(X,M =
2.3.4.- fbEs Prediction Equation
exp
llatl
50.26
(cos X)
0.73
10)
The single term which remains to be determined is the constant of proportionality (A) which
takes into account the cos X, R and P(X,^ ) coefficients which have not been chosen inde-
pendently. Then;
C - 93
A= fbEs(obs)./cos"XfF(R).F(X,A )
(11)
Figure 7a shows the A value for the four latitudes under study for all R and cos X values,
while Fig. 7b shows A value as function of cos X values, for all latitudes and R values.
H H ,.
MEHN R s= 3 . BHH
DEV . = 0 . I IH
20
30
H0 S0
I_R-T I TUDE
;z
T
H
MERN R =3 . BHH
i
^_^_ ~~- *"
i
, ^ ^— ~~"
i
3
S . PEV . =0 . 2B
i
a
0 . 2
0 . S .V .31.0
ens x
Fig. 7.- Experimental
values on the proportio-
nality constant to be
adopted in order to ob-
tain a good fbEs value.
Crosses indicate mean
value of the proportio-
nality constant averaged
on cos X values, an R
number for the fall set
of data, for each station
(upper figure). Crosses
indicate mean values of
A averaged on latitude
and solar activity for
the full set of data
for each cos X value cells,
to make the equation (11) easier to handle, the X variable might be replaced by local time,
with the help of the declination equation:
o = 23.45 sin jj60 (n + 284°)
365
(12)
where n + number of the day of the year
and cos X(o ,A , local time) equation:
cos X
* sind sinA + cosd cos^ cos h
13)
where h = number of the hour x 36O0 - l8o°
24
Results
Fig. 8 shows the comparison between experimental and calculated frequency values as:
(fbEs -fbEs ) /fbEs (14)
observed calculated observed
for the South American sector under study, as mean values over cos X, for all the period
considered. _
C - 94
IB
3
.- -IB
2MB R CHQJ]
Fig. 8.- Estimation
of the relative error
of the method for the
South American sector
for the four stations
under study (crosses)
it have been obtained
by calculating equa-io
tion (14) for each da-
ta column and each sta-
tion for solar R va-
lues = 20, 50, 100,
150 and 200.
3.- BASES FOR TECHNIQUE
The empirical formula obtained to reproduce experimental values is based on physical argu-
ments for the selection of the variables and on mathematical and statistical arguments to
obtain the equations.
The selection of R, X and A as variables, is based on the dependence of Es layers on Nor-
mal E layer ionization for reasons already mentioned in the introduction, for the two first
variables (R and X); and in the special nature of Es formation (neutral wind-shears) for
the third variable (latitude).
As Sporadic-E layer formation in a particular isolated case depends on meteorological con-
ditions prevailing in E region heights (Whitehead, 1972), it is impossible to predict iso-
lated cases, but a mean value of several cases, eliminates to a certain amount, the parti-
cular and ocassional conditions surrounding each case, and leaves only the general pattern,
which is predicted in this pap«*. This prediction of »edfc»n hourly values for fbEs Is based
on the assumption of predictability of mean conditions for the data of a whole month.
4.- SAMPLE PREDICTIONS
Median hourly values published In "ionospheric Data" booklets for fbEs are used as experi-
mental data in the foregoing section for the world wide test of the method.
C - 95
i
LBT.i:-23.S0LDNG.s-HG,S0
12 IB
LOCBL TIME
RCWOLFls 161. BB
UTT . e-23 . 50LONE . s-H6 . 50
RCHOLFfe IEI.00
LBT.e-Z3.£0LDNE.=-4G.S0
12 IB
LOCBL TltC
12 IB
LOCBL TIME
12 IB
LDCBL TIME
rcmolfsb mi. 00
LBT . s-2S . 90LONB . s-BS . H0
12 IB
LOCBL TIME
OBTEb 6/ I3S9
RCHDLFSs IGI.00
LBT.B-2E.B0LONG.s-ES.M0
12 IB
LOCBL TIME
r.H
12/ I!
RCMOLFSs 132.00
LBT . s-3H . 50LONG . s-SB . 50
12 IB
LOCRL TIME
l>BTEe 3/ I!
RCH0LF3C I7H.00
LBT . s-3M . 50LONE . =-SB . SB
DBTEs E/ 1953
RCWOLFUs IGI.00
LBT . s-3M . 50LONG . =-SB . 50
12 IB
LDCBL TIME
12 IB
LDCBL TIME
r.H
DBTEs 12/ 1959 g
RC WOLF 3s 132.00 g
LBT . s-S I . 70LONG . e-S7 . 00 E
12 IB
LDCBL TIME
^^^»
• .
/•
• ^^
/•
• \
7 DBTEs
3/
1959 \
J RC WOLF 3s
I7H.00 j
)LbT.s-SI.
70LDNE.~S7.BJf
r.H
jTODLFfe I
LBT.4-SI.70LDNE
7.B0
12 IB
LDCBL TIME
12 IB
LOCBL TIME
Pig. 10.- South American Sector, the same as Fig. 9 but for high solar
activity level
C - 98
r-H
0
i
6
I
DRTE= 1/ I9S7
RCW0LF3= 170.00
LRT.=-27.S0LONE.= IS2.90
• ^V
«
/ •
1
DRTE= 3/
I9S7
RCWOLfk
I7H.00
LRT
.=-27.50LONE.= IS2
90
mH
12 IB
LDCRL TIME
12 IB
LDCBL TIME
RC^DLF3= B0.00
LRT . — 3H . I 0LONE . = IB. 30
- 0
^^^»
•
•
^^ •
•
0 / •
DRTEs
3/
1371
\*
RCWOLI
-fc
7H.00
LHT
.=-3H.
I0LDNE.=
IB
.30
0
1
DRTE= E/ 1957
RCWDLF3= IBB. 00
LRT.=-27.S0LDNE.= IS2.90
12 IB
LDCBL TIME
. 0
!CWDLF1= E7.00
LRT.=-3H.I0LDNE.= IB. 30
12 IB
LDCBL TIME
12 IB
LDCRL TIME
12 IB
LDCRL TIME
^H
§2
,-,H
DRTEs 1/ I9BB .\.^2
RCWDLFDn 103.00
LRT.=-30.B0LONE.r I3E.30 E
0
DRTEs 3/ I9EB
RCUOLFfe 105.00
LRT.=-30.B0LDNE.= I3E.30C
0RTE= E/ I9EB
RCWDLFDs 107.00
.=-30.B0LDNS.= 13$ 32
12 IB
LDCRL TIME
12 IB
LDCRL TIME
12 IB
LDCRL TIME
H
DRTE= 1/ I97E
RC WOLF In B. 10
LRT.=-3H.M2LDNB.= 19.23
DRTEr 9/ I97B
RCWDLFDc 13. SB
TT.=-3M.M2LDNE.= 19.23 £
:WDLF3= IS
LRT.=-3H.H2LDNE.=
12 IB
LDCRL TIME
6 12 IB E 12 IB
LDCRL TIME LDCRL TIME
Fig.- 11.- Australia and South Africa. Dotts: observed median hourly va-
lues (MHz); full line: predicted values (MHz). From left to right, Summer
Equinox, Winter; from top to bottom, Brisbane (Australia); Capetown ( S. A-
frica); Woomera (Australia) and Hermanus ( S. Africa). Date = month/year;
R (Wolf) = R sunspot value; lat. - long. = geographic latitude and longitude.
99
n*
DHTEc 1/ 1372
RCHOLFfc 71.00
LRT.s-H3.60LON6.s 172.
i » ■ » ■■» ■<■»■ 0— «
DHTEc 9/ 1972
RCHOLFfc 62.00
LHT.C-M3.S0LONS.S: 172.
01—
12 IB
LOCHL TIHE
12 IB
LOCHL TIHE
6/ 1973
:HQLF3e 39.00
LHT.c-H3.60LON5.c 172. BJ
Hi—
12 IB
LOCHL TIME
DHTEc 12/ 1967
RCHOLFk 101.00
LHT.c-30.B0LON6.c 136.30
*— ^p— ^
>• . •
• 7v
•
• ^
/ ♦
• 1
DHTEc 3/
I96B
•
RCMOLFSc
105.00
LHT
.P-30.B0LON6.B 136
.30
1
12 IB
LDCBL TIHE
12 IB
LOCHL TlfC
«^— ^— ^ .4— — r— 4
12 IB
LOCHL TIME
DHTEc 1/ 1971
RCHOLFl= 80. BB
LRT.c-M9.H0LOJC.c-70.30
r,H
LHT . c-H9 . H0LON6 . e-70 . 30
DHTEe 6/ I97l\
(*CVCLF3= 67.00**
LHT :=-H9 . H0LON6 . =-70 . 30
12 IB
LOCHL TIME
12 II
LOCHL TIHE
12 IB
LOCHL TIHE
Fig. 12.- Australian sector; from top to bottom Christchurch, Woomera
and Kerguelen.
C - 100
RCM0LF3b 10*7. 00
LRT.s 23.00UlNE.s-B2.IB
12 IB
LOCRL TIME
RCWDLF1= IS. 00
LRT.s 23.00LONG.s-B2.IB
12 IB
LOCRL TIME
12 IB
LDCBL TIME
DRTEs 7/ 1972
RCHOLFfc: Efl.00
LRT.s 32.20LONS.s-l0E.S0
12 IB
LOCAL TIME
DRTEs H/ 1972
RC WOLF 3s 73. 00
ILRT.s 32.30LONE.s-l0E.S0 £
RCM0LF3s 70.00
LRT.s 32.3BLONE.s-l0E.S0
12 IB
LOCRL TIME
12 IB
LOCRL TIME
i
«-■
DRTEs E/ 1973
RCHDLF-fc 39.00
LRT.s H0.00LONE.s-l0S.30
12 IB
LOCRL TIME
RCW0LF3s 3S.00
LRT.s H0.00LONE.s-l0S.30
.30
12 IB
LOCRL TIME
12 IB
LOCRL TIME
r,H
r.H
DHTEs EV 1973
RCHOLFJe 39.00
LRT.s H9.B0LONG.s-9H.H0
12 IB
LOCRL TIME
/
•
^
• •
/
•
/ •
/.
DRTEs
B/
1972
• \
RC WOLF 3s
EE.00
LRT
.s H9.
B0LONE.S-
9H
H0
r.H
LRT.s H9.B0LONE.s-9H.HB
12 IB
LOCRL TIME
12 IB
LOCRL TINE
Pig. 13.- North American sector. From top to bottom Cuba, White Sands,
Boulder and Winnipeg. Dotts: observed median hourly values (MHz); full
line: predicted values (MHz) legends with the same meaning as fig. 9
and 11.
C - 101
r.H
DBTEs 6/ 1373
RCHOLFk: 33.00
LRT.s IH.70LDNB.s-l7.'
r^H
DRTEs 3/1371
RCWOLFls 66.00
LRT.s IH.70LON6.s-l7.H0
RCHDLF3s 71.00
LRT.s IH.70LONB.s-I7.H0
12 IB
LOCRL TIME
12 IB
LOCAL TINE
12 IB
LOCHL TINE
• • •
H
2
/ DRTEs 6/ 1360 \
RCH0LF3s IIH.00
LRT.s 30.30LON6.S B.B0
0
r.H
RCH0LF3s 102.00
LBT.s 30.30LONE.S E.B0
1
RTWOLFfc 33.00
LPT.s 30.S0LONB.S E.B0
12 IB
LOCPL TINE
12 IB
LOCRL TINE
12 IB
LOOM- TINE
i
DRTEs 7/ 1370
RCH0LF3s I0H.00
LBT.s H0.B0LON6.S 0.00
r,H
32
RCMOLFSs 66.00
UTT.s HB.BflkONE.s 0.
RCMDLF3s HE. 00
LHT.s H0.B0LONE.S 0.00
12 IB
LOCRL TINE
12 IB
LOCBL TINE
12 IB
LOCBL TINE
DRTEs 6/ 1373
RCHOLFls 33.00
LRT.s SI.S0LONE.S 0.E0
0L-~
r.H
DRTEs 3/ 1373
RCMOLf 3s 3S.00
LBT.s SI.50LONE.S 0.6E '-
0l
12 IB
LOCRL TINE
12 IB
LOCRL TINE
12 IB
LOCBL TINE
Fig. 14.- Europe and North Africa. Prom top to bottom Dakar, Rabat,
Portosa and Slough; legends similar to figs. 9 and 11.
C - 102
r^H
RCWDLFJe 106. 00 u
LBT.s 22.3BLDNE.S I IS. IB E
'.IB
12 IB
LOOK. TIME
r,H
2 /
l>BTEs B/ IB73
RCHOLFDs SB. 00
LRT.s 3I.2BL0NG.S 130
12 IB
LDCBL TIME
DRTEs B/ I!
RCHDLFJs IBE.BB
LHT.= S1.3BL0NG.S B9.30
12 IB
LDCRL TIME
r.H
DBTEs E/ 1969
RCMOLFfe IBB.BB
LBT.s H9.B0LDNG.= 73. IB
12 IB
LDCBL TIME
12 IB
LOCHL TIME
12 IB
LDCBL TIME
r,^
RCMOLFSc BE.BB
UTT.s 2B.EBU3HE.S 77. 2B
. RCHOLFfe 5B.BB
LBT.s 2E.3BL0NG.5 127.
12 IB
LDCBL TIME
12 IB
LOCBL TIME
r.H
r.H
K
RCWDLF3= 103.00
LBT.s Sl.30LDNS.= E9.30
12 IB
LDCBL TIME
12 IB
LDCRL TIME
r,H
DBTEs 9/ I9EB
RCWDLFfc IB7.BB
LBT.s SS.BBLDNE.s 73. IB
'WTTEb 2/ I!
RCUDLFDc 1 03. 00
LBT.s S9.B0LDNG.S 73. IB
12 IB
LDCRL TIME
12 IB
LDCRL TIME
Fig. 15." Asia (Northern Hemisphere). Legends similar to figures 9 and
11. Top line (3 figures) from Hong Kong. Second line from top: left Oki-
nawa, center Delhi, right Yamagawa. Third line from top: Tashkent, bottom
Karaganda.
103
5.- CONCLUSIONS
The prediction method presented reproduces within a reasonably good margin the observed
daytime fbEs data for ionospheric stations between 20° and 40° latitude (North and South
Hemispheres). There is observed that fbEs values might be' predicted as function of month
number, solar activity level and geographical latitude, as is suggested by theoretical and
experimental evidence of Es layers dynamics. For latitudes higher than 40° during Winter
time, the prediction method is not adequate nor for latitudes where Dip angle is higher
than - 50 • The empirical formula reached have a strong resemblance with the corresponding
foE prediction formuli in the terms corresponding to solar zenith angle and solar activi-
ties parameters. There is a third term, a latitudinal term, wlch does not appear in foE
prediction, but that is of fundamental importance for Sporadic-E prediction formuli, due
to the formation mechani sm wh i ch is its distinct characteristic.
BIBLIOGRAPHY
Anderson, J. G. , and C. A. Barth (1971): Rocket investigation of the Mgl and Mgll dayglow
J.G.R. 76, 3723 - 3732.
Axford, W. I. (196l): Note on a mechanism for the vertical transport of ionization in the
ionosphere. Can. J. Phys. 39 , 1393.
Axford, W. I. (1963): The formation and vertical movement of dense ionized layers in the
ionosphere due to vertical wind-shear. J. G. R. 68, 769-779.
Baggaley, W. J., and C. H. Cummack (1974): Meteor train ion chemistry. J.A.T.P. 36, 1759-
1773.
Behnke, R. A., and J. P. Vickrey (1975): Radar evidence for Pe+ in a Sporadic-E layer.
Radio Sci. 10, 325-327.
Bossolasco, M. , and A. Elena (1963): Sporadic-E layer ionization and the sunspot cycle.
Geofls. pura appl. 56 (3), 142.
Bowen, P. J., K. Norman, A. P. Willmore, J. M. Baguette, F. Murtin and R. 0. Storey (1964):
Rocket studies of Sporadic-E ionization and ionospheric winds. Planet. Space Sci. 12,
, 1173.
Brown, T. L. (1973): The chemistry of metallic elements in the ionosphere and mesosphere
Chem. Rev. 73, 61+5-667.
CCIR Doc 6/177-E (1976): Report 259-3 (Rev. 76) VHF propagation by irregular layers, Spora-
dic-E or other anomalous ionization. 230-259.
CCIR Doc 6/177-E (1976): Question 4-1/6 (Rev. 76) Propagation by way of Sporadic-E and
other anomalous ionization. 349.
CCIR Study programms 4A-2/6 and 4B-2/6, 249, CCIR Comlssion VI (1974).
Chimonas, G. , and W. I. Axford (1968): Vertical movement of temperate-zone Sporadic-E lay-
ers. J. G. R. 73, III-II7.
Davles, K. (1965): Ionospheric radio propagation. NBS Monograph 80.
Evans, J. V. (1976): The dynamics of the ionosphere and upper atmosphere. AGU - ISSTP,
Boulder, Co. Vol. II.
Ferguson, E. E. (1972): Atmospheric metal ion chemistry. Radio Sci. 7, 397-401.
Goldberg, R. A. (1975): Silicon ions below 100 km: A case for SlOg. Radio Sci. 10, 329-334.
Hall, R. B. (1964): The formation of the Sporadic-E layer. J. A. T. P. 26, 1143-1146.
Harper, R. M. , R. H. Wand, and J. D. Whitehead (1975): Comparison of Areclbo E-reglon data
and Sporadic-E theory: A measurement of the diffusion coefficient. Radio Sci. 10,
357-62.
C - 104
Heisler, L. H. , and J. D. Whitehead (1964): The correlation between the occurrence of Spo-
radlc-E and the horizontal component of the earth's magnetic field. J. A. T. P. 26.
439~444.
Hines, C. 0. (1963): The upper atmolphere in motion. Quart. J. Roy. Meterolog. Soc. 89,
1-42.
Hines, C. 0. (1964): The formation of midlatitude Sporadic-E layers. J. G. R. 69 , IOI8-9.
Istomin, V. G. , (1963): Ions of extra-terrestrial origin in the earth's ionosphere. Space
Res, J, 209-220.
Johanessen, A., and D. Krankowsky (1972): Positive-ion composition measurements in the upper
mesosphere and lower thermosphere at high latitude during Summer. J. G. R. 77, 2888-
2901.
Lindzen, R. S. (1974): Tides and internal gravity waves in the atmosphere. P. Vernianl (ed)
Structure and dynamics of the upper atmosphere. Elsevier Press, N. Y. , 1974.
MacLeod, M. A. (1966): Sporadic-E theory; collision-geomagnetic equilibrium. J. Atmos.
Scl. 2}, 96.
Miller, K. L. , and Smith, L. G. (1975): Horizontal structure of midlatitude Sporadic-E
layers observed by incoherent scatter radar. R. Scl. 10, 271-276.
Miller, K. L. , and L. G. Smith (1976): Midlatitude Sporadic-E layers. Aeronomy Report 76,
Univ. of Illinois.
Narcisi, R. S. , and A. D. Bailey (1965): Mass spectrometric measurements of positive ions
at altitudes from 64 to 112 km. J. G. R. JO, 3687-37OO.
Narcisi, R. S. (1968): Processes associated with metal ion layers in the E- region of the
ionosphere. Space Res. 8, 360-369.
Narcisi, R. S. (1973): Mass spectrometer measurements in the ionosphere. Phys. and Chem.
of Upper Atmosphere, B. M. McCormac (Ed.), D. Reidel Publ. Co. Dordrecht, Holland,
171-183.
Poole, L. M. G. , and T. F. Nicholson (1975): The effect of ionic processes on the charac-
teristics of radio echoes from meteor trains. Planet. Spa. Scl. 23, 1261-1277.
Rawer, K. (1962): Structure of Es at temperature latitudes. Ionosp. Sporadlc-E, E. K.
Smith and S. Matsushita (Ed.), Mc Mil Ian Co. N. York, 292-343.
Reddy, C. A., and M. Rao (1968): On the physical significance of the Es parameters fbEs,
fEs, and foEs. J. G. R. £3.» 215-224.
Reddy, C. A. and Matsushita, S. (1968): The variations of neutral wind shears in the E-re-
gion as deduced from blanketing Es. J. A. T. P. _3_0, 747-762.
Reddy, C. A. and Matsushita, S. (1969): Time and latitude variations on Blanketing Es of
different intensities. J. G. R. 74, 824-843.
Richmond, A. D. (1971): Tidal winds at ionospheric heights. Radio Scl. 6, 175-189.
Richmond, A. D. (1977): Ionospheric winds: Dynamo theory: A review. Submitted to J. Geomag.
Geoelect. (Japan).
Richmond, A. D. , S. Matsushita and J. D. Tarpley (1976): On the production mechanism of e-
lectric currents and fields in the ionosphere. J. G. R. 8l , 547-555.
Rosenberg, N. W. , and H. D. Edwards (1964): Observations of ionospheric wind patterns thro-
ugh the night. J. G. R. _6_9_, 2819-2826.
Rosenberg, N. W. and H. D. Edwards, and J. W. Wright (1964): Ionospheric winds; motions
Into night and Sporadic-E. Space Res. 4, 171.
Smith, L. G. , and Miller, K. L. (I977): Sporadic-E layers and unstable wind-shears. Sub-
mitted to J. of Geomag. and Geoelect. (Japan).
Swider, Jr., W. (1969): Processes for meteorltic elements in the E-reglon. Planet. Space.
Scl. lj, 1233-1242.
Volland, H. , and H. G. Mayr (1972): A three dimensional model of themospheric dynamics: I,
II and III. J. A. T. P. ,3_4 , 1745-1816.
Volland, H. , and H. G. Mayr (1974): Tidal waves within the thermosphere. R. Scl. 9, 263-73.
C - 105
Volland, H. , and H. G. Mayr (1977)s Theoretical aspects of tidal and planetary wave propa-
gation at t he rmo spheric heights. Rev. Geophys. Space Phys. 15, 203-225.
Volland, H. , and L. Grellmann (1977): A hydromagnetic dynamo of the atmosphere. Submitted
to J. Geomag. Geoelect. ( Japan) .
Whitehead, J. D. (i960): Formation of the Sporadic-E layer in the temperate zones. Nature
188, 567.
Whitehead, J. D. (1961): The formation of the Sporadic-E layer in the temperate zones.
J. A. T. P. 20, 49-58.
Whitehead, J. D. (1962): The formation of a Sporadic-E layer from a vertical gradient in
horizontal wind. Ionos. Sporadic-E, Smith, E. K. , and Matsushita, S.
Whitehead, J. D. (197°) 5 Production and prediction of Sporadic-E. Rev. Geophys. Space
Phys. 8, 65-144.
Whitehead, J. D. (1972): The structure of Sporadic-E from a radio experiment. Radio Scl. 7,
355-358.
Wright, J. W. (1967): Sporadic-E as an indicator of wind structure in the lower ionosphere
and the influx of meteors. J. G. R. 72, 4821-4830.
Wright, J. W. , C. H. Murphy and G. U. Bull (1967): Sporadic-E and the wind structure of
the E- region. J. G. R. Jl> 1443-1460.
Wright, J. W. , and L. S. Fedor (1969): The interpretation of ionospheric radio drift measu-
rements, 2. Kinesonde observations of micro structure and vertical motion of Sporadic-
E. J. A. T. P. jl, 925.
Young, J. M. , C. Y. Johnson and J. C. Holmes (1967): Positive ion composition of a tempera-
te-latitude Es layer as observed during a rocket flight. J. G. R. 72, 1473-1497.
Zbinden, P. A., M. A. Hidalgo, P. Eberhardt and J. Geiss: (1975) Mass spectrometer measure-
ments of the positive ion composition in the D- and E-regions of the ionosphere.
Planet. Space Scl. _2J, l621-l624.
106
SHORT TERM PREDICTION OF IONOSPHERIC DISTURBANCES
S. N. MITRA
Al 1 India Radio
Akashvani Bhavan
Pari iament Street
New Delhi 110001, INDIA
MANGAL SAIN
All India Radio
Research Department
Indraprastha Estate
New Delhi 110002, INDIA
The CCIR in its Study Program 10A-1/6(1974) has asked for indentifi-
cation of precursors to forecast short-term disturbances of the ionsphere
arising out of solar phenomena. The only solar happening that can cause
ionospheric disturbance is a flare on the sun's chromosphere and its
accurate observation will be needed to make such short-term forecasts of
propagation conditions which may be needed for the development of appro-
priate Technical Standards used by I FRB (Recommendation 4, RR) . A method
for such forecasts is described in this document.
A simple, reliable and unambiguous radio method of detecting a flare
through propagation of longwaves was developed in the Research Department
of All India Radio in August, 1958 (Mitra, 1959) at Delhi (77°05'E, -
28°35'N). This method, based on the continous recording of field strength
of a distant longwave station, makes use of the fact that a sudden change
occurs in longwave signal during a solar flare. This effect has been
designated as SCL (Mitra, 1970). An explanation for the above-mentioned
changes in longwave intensity has^offered (Mitra, 1970, 1973, 1974).
Based on extensive field strength recordings at Delhi (77°05'E, -
28°35'N) of Radio Tashkent (69°22'E, 41°25'N) operating on 164 kHz at a
distance of 1630 Km from Delhi and Radio Alma - Ata (77°00'E, 43°17'N)
operating on 182 kHz at a distance of 1660 Km from Delhi, it has been
established that this method is very effective for the detection of solar
flares (Mitra, 1964, 1973, 1974). A procedure for classification of solar
flare* detected by this method has been suggested (Mitra, 1964).
A practical utility of the SCL observation of a solar flare is in
short-term forecasting of magnetic storms, a delayed effect caused by
corpuscular emissions from flares,. Such magnetic storms affect adversely
shortwave propagation and an accurate forecast would be important for radio
communications. The magnetic storms are caused by the incidence of charged
corpuscles emitted during a flare when they impinge upon the ionosphere
with concentration lit the polar regions. The beginning of the storm will
depend upon the arrival of these particles, which in turn depends upon
their speed of travel. Data on principal magnetic storms collected during
I GY (1958-60) recorded at Alibag (India) Magnetic Observatory have been
analysed with a view to finding the most probable delay (Mangal Sain, 1968)
Figure 1 shows one such histogram where this delay is found to be 23 hours.
107
FIGURE 1.
in
Ui
o
Z
Ui
a
a
D
O
o
o
L.
o
o
2
HISTOGRAM SHOWING THE DELAY BETWEEN THE BEGINNING
OF SILs AND BEGINNING OF CORRESPONDING MAGNETIC STORM.
16
12
n
16
20
24
28
32
36
40
44
48
A study has also been made to determine the most probable value of
the duration of a magnetic storm corresponding to an SCL and it has been
found to be 26 hours (Figure 2). However, when SCL's corresponding to
type 3 and 3+ flares are only considered, the duration is 34 hours.
24 r
III
a )6
2
ui
or
a.
:>
u
u
Z '
o
6
z
n-r-r-i
>6 24 32 40 48 56 64 72 80 88
DURATION OF MAGNETIC DISTURBANCE IN HOURS ►
Figure 2. Histogram showing the Duration of Magnetic Storm for all types
of Flares observed through Sil.
108
On further analysis, it has been observed that the probablity of
occurrence of a magnetic storm is high where the relative increase in
signal in an SCL is large. Any increase by 10 dB or greater is very
likely to be associated with a magnetic storm within 20 to 24 hours of its
occurrence. A systematic world wide patrol and study of SCL could provide
a useful tool for short term prediction of ionosheric disturbances and the
resulting propagation conditions.
REFERENCES
Mangal Sain. (1968): Ph. D. Thesis on 'Investigation of Lower lonoshere
through the Study of Longwave Propagation and SID
Effects', submitted to the University of Delhi (India)
Mitra, S. N. (1959): Some Investigations on Longwave Propagation, J . Inst.
Elec. Telecomm. Engrs (India) , 5 , 121.
Mltra, S. N. (1964): A Radio Method of Dectecting Solar Flares,
J. Atmos. Terr. Phvs. . 26, 35.
Mitra, S. N. (1970): SCL - A New Nomencature to Denote the Effect of
Solar Flares on Longwave Propagation Intensity,
Solar Physics. 15 , 249.
Mitra, S. N. (197 3): SCL and its Associations with Solar 6 Geophysical
Activity, Indian Journal of Radio and Space Physics,
2 , 193.
Mitra, S. N. (1974): SCL and its Dependence on Season and X-ray Flux
Density From a Solar Flare, J. Inst. Elec. Telecomm.
Engrs (India) . 20, 141.
C - 109
THE INFERENCE OF SEVERE NIGHT-TIME DISTURBANCES OF
THE D REGION FROM HIGH-LATITUDE RIOMETER OBSERVATIONS
J.K. Hargreaves
Ionosphere and Magnetosphere Unit
Dept. of Environmental Sciences
University of Lancaster
Lancaster
LAI 47Q
England
The short-duration "spike" events, often seen at the beginning
of substorms with high-latitude riometers, are much more intense
than is indicated by measurements with a standard wide-beam riometer
system. The ionospheric event may be less than 50 km across, but the
electron density at 90 km may rise to over 106 cm-3 in less than a
minute, leading to strong horizontal gradients of electron density.
The local energy input to the D-region is considerable during these
events. A real-time system for the rapid detection of the events is
proposed, based on the use of riometers with different beamwidths.
The auroral D and E regions are sometimes perturbed by precipitation
events of quite remarkable intensity, in which the electron density at 90 km
altitude may for a short time exceed 106 cm-3. The events occur most
frequently during the few hours before midnight, and are most easily recog-
nized on a riometer record where they appear as sharp-onset "spike events".
In some cases the spike clearly marks the beginning of a substorm, but at
other times it occurs in isolation. It does not usually appear after a sub-
storm has been in progress for several minutes, however.
The properties of the spike event are unusual by comparison with other
precipitation events. Not only is it particularly intense, but also it is
more spatially confined than most other auroral absorption events and is
subject to more rapid motion — generally, like the substorm onset, in a
poleward direction.
Figure 1 shows an example of such an event as observed by incoherent
scatter radar from Chatanika, Alaska. This event rose to a maximum in 20 sec
and its duration between electron densities of half the peak value was also
20 sec. (Figure la). At the peak of the event the electron density was
106 cm-3 at 90 km and over 2xl06 cm"3 at the layer maximum at about 98 km
C - 110
Ck,
»U..k« wj gf i«il ijjg M
**.l.
I ' ' ■ ■ f ' ' ' ' I ■ ' '',.-■ ,
» u u U. T. i> 11 lo
1. SPIKE EVENT SEEN AT CHATANIKA ON 1975 NOV 29.
(a) ELECTRON DENSITY AT FIXED HEIGHT. (b) ELECTRON DENSITY PROFILE AT THE
PEAK OF THE EVENT.
(Figure lb). At the same time the 30 MHz riometer at Chatanika registered a
spike absorption event with maximum absorption 3.0 dB. Recent studies
(Nielsen and Axford, 1977; Hargreaves, Chivers and Nielsen, 1979.) have
shown that the spike events are narrower than the region observed by a
standard wide-beam riometer antenna and typically, if represented by a
gaussian model, have a characteristic width (xq) of some 20 - 40 km if the
absorbing layer is at 90 km altitude. (The relatively narrow width explains
why there is a marked discrepancy between the observed and calculated absorp-
tion values, 3.0 and 13.8 dB respectively, for the event of Figure 1.)
The intensity of the spike event as a disturbance of the D and E regions
makes it a phenomenon of some interest. For instance, assuming the variation
of event intensity seen at a fixed site to be due to movement of the precipit-
ation region, the spatial distribution of D- and E-region ionization can be
estimated for a typical case (width Xq = 30 km, peak electron density 106 cm"3
at 90 km altitude). As shown in Figure 2, the contours of constant electron
density may be considerably tilted during the passage of the disturbance. The
ionospheric event corresponds to large field- aligned fluxes of energetic
(above 20 kev) electrons at geostationary orbit, and the energy deposition
below 90 km can reach 40 erg/cm2-sec.
111
CLU-,.. A^v.h, Cc*;>)
** ** -. ^ ^ -.
*>-
twii.*r»i XtK»«cw«)
ro
2. ESTIMATED SPATIAL DISTRIBUTION OF ELECTRON DENSITY IN A SPIKE EVENT,
WITH HORIZONTAL AND VERTICAL DISTANCES PLOTTED ON THE SAME SCALE. A
GAUSSIAN VARIATION OF ELECTRON DENSITY AT GIVEN HEIGHT HAS BEEN ASSUMED.
The spatial confinement of the events provides a possible method for their
rapid detection, using riometers with antennas of different beamwidths.
Calculations have been made of the response of various riometer antennas to
absorption events in the form of a gaussian strip, in which the absorption
varies as Aq exp (~x2/2x02) in the x-direction but with no variation in the
y-direction. Figure 3 compares the responses due to a wide-beam antenna of
width 64° between half-power points, B(l), and a "medium-beam" antenna of
beamwidth 32°, B(2). It is seen that the ratio of the responses, B(2)/B(l),
as a function of B(l) provides an estimate of the width, Xq, as well as of the
true intensity of the event, Aq. (The true intensity is the absorption that
would be measured by a riometer with a zenithal pencil-beam antenna.) For
most events, a ratio exceeding 1.3 will indicate a narrow event, whereas for
widespread absorption events the ratio will be less than unity.
Operationally, the above possibility could be implemented using the I. M.S.
riometer chain in Alaska, whose output is transmitted to the Space Environment
Laboratory, Boulder, almost in real time (actually at 12-minute intervals) .
In addition to the construction of a riometer system with narrower antenna
beam in Alaska, computer software would have to be developed to convert the
riometer readings to absorption values and then to derive the ratios B(2)/B(l)
112
3. RATIO OF APPARENT ABSORPTION WITH WIDE (B(l)) AND MEDIUM (B(2))
RIOMETER ANTENNAS, BASED ON A GAUSSIAN STRIP MODEL, THE WIDE AND
MEDIUM ANTENNAS HAVING BEAMWIDTHS OF 64° AND 32° RESPECTIVELY.
THE RATIO WOULD BE ABOUT 2 FOR THE EVENT OF FIGURE 1,
COMPARED WITH UNITY OR LESS FOR A WIDESPREAD EVENT.
continuously. Such a system would provide a rapid warning of intense,
spatially confined, auroral precipitation events. It is suggested that such
a system might also provide the possibility of early detection of substorm
occurrence. The chance of a substorm following a spike event is fairly high,
and although the actual probability is not known this could be readily
evaluated from existing data.
Acknowledgements
I am indebted to the radar group at the Aeronomy Center, Utah State
University, for making available observations from Chatanika, to Drs. H.J. A.
Chivers and E. Nielsen for discussions on spike events, and to Mrs. S.
Hargreaves for assistance with the computations.
References
Hargreaves, J. K. , H. J. A. Chivers, and E. Nielsen (1979): Properties of
spike events in auroral radio absorption. J. Geophys. Res., 84, 4245.
Nielsen, E., and W.I. Axford (1977): Small-scale auroral absorption events
associated with substorms. Nature, 267:502.
113
THE POSSIBLE PREDICTION OF SID'S USING THE SLOWLY VARYING
COMPONENT OF THE SOLAR RADIO FLUX AT 3-2CM
Zhu Zu Yan, Zhou Ai Hua, and Zhou Shu Rong
Purple Mountain Observatory, Nanking, China
1. INTRODUCTION
There is a fairly good correlation between SID's and the slowly varying
component (SVC) at 3.2cm. Using the solar radio total flux density at 3. 2cm
and the data of sudden disturbance in the ionosphere, the statistical
correlation was made. It has been found that the relative continuous
increase of SVC at 3-2cm can be used to predict SID events.
2 . DATA
The radio data used were the daily antenna temperature observed with the
3.2cm radio telescope of the Purple Mountain Observatory. The activities
of all solar active regions on the solar surface contribute to the peaks and
valleys of the curves of variation of daily antenna temperature.
The SID data are the records of communication circuits in our country
during December 1 966 to February 1975. According to the coincidence between
3.2cm solar bursts and communication events, the latter can be identified as
SID events. The SID events which took place during periods of no solar
observations were not used.
3. THE POSSIBLE PREDICTION METHOD
According to the variation of daily antenna temperature, we judged
the possibility that solar bursts would occur that give rise to SID events.
An analysis of 95 peaks on the antenna temperature curves was made, and the
relative continuous increase of antenna temperature for each peak,
(Ta-Ta)/Ta or (Ta-Ta)/Ta, was calculated, where Ta and Ta are antenna tempera-
ture values observed on the third and fourth days, respectively, after the
beginning day tQ of successive antenna temperature increase. Comparing the
calculated values with SID data, the results are given in Figure 1, where
dots indicate that there are SID events during the peak period and circles
indicate no SID at all. It has been found that the peaks corresponding to
SID events satisfy the following criteria:
C - ]\k
(Ta-Ta)/Ta > 5-5%
or
(Ta-Ta)/Ta > 1.0%
and most of the dates which have SID events occur within seven days later
than the date on which the foregoing criteria are satisfied. Then we
obtained the prediction criteria: when the relative continuous increase of
antenna temperature satisfies the criteria
(Ta-Ta)/Ta > 5-5%
or
(Ta-Ta)/Ta > 1.0%
there will appear SID events within seven days caused by solar bursts.
The data was analyzed for 98 days of SID's. Consider Figure 2, where
At indicates the days between the date of an SID and the date of the pre-
ceding valley of the radio flux curve. The vertical coordinate indicates
the number of days with SID events. It can be seen from Figure 2 that most
SID events take place within 7 days after satisfying the criteria (from the
3rd to 9th days), which is 76.5% of the total days of SID events. There is
only 18.4% At in 6 days (10th to 15th days) and 5-1% At in 1st - 2nd and
1 6th - 17th days as shown in Table 1.
25
o
ro
£ 20
o
d)
Q.
15
o
T 10
5.5
• with SID events
o no SID event
A indicates(T04-Ta°)/T00
A
o •
o • •
o
o
• A
•o A
0 o
o o •
o__ -a-
Jo o
00
10 20 30 40 50 60
Series Number of Peak
70
80
90
100
Figure 1. Distribution of three-day percentage change in the
slowly varying component of 3-2cm solar radio flux.
115
Table 1.
Time Interval
At (days)
l-17(day) (total days)
1-2 (2 days)
3-9 (7 days)
10-15 (6 days)
16-17 (2 days)
days with
SID
days
with SID
98
100
3
3.1
75
76.5
18
18.4
2
2.0
2 3 4 5 6 7 8 9 10 I 12 13 14 15 16 17
At (days)
Figure 2. Distribution of SID's.
C - 116
D. RADIO PROPAGATION PREDICTIONS
1. TRANS IONOSPHERE PROPAGATION PREDICTIONS
AN IMPROVED IONOSPHERIC IRREGULARITY MODEL
D.G. Singleton
Defence Science and Technology Organization,
Electronics Research Laboratory,
Salisbury, S.A., Australia
Modifications are made to the global model developed by Fremouw
et al. for the incremental electron density of F-layer
irregularities in order to force the model into agreement with a
considerable body of scintillation and spread-F data. While
special attention is given to the equatorial region, where the
original model was particularly lacking, the results of other
studies are used to update the model in the other latitude regions
and so provide a model of general application.
1. INTRODUCTION
Fremouw and Bates (1971) and later Fremouw and Rino (1973) were the first
to attempt to produce an irregularity model by collating the data available
in the literature on the occurrence, strength, size, etc. of F-region
ionization density irregularities. They proposed an empirical model of
global scintillation behaviour taking into account variations due to time of
day, season, sunspot-cycle and latitude. An extension of this model to
allow simulation of spread-F occurrence as well as scintillation index was
proposed by Singleton (1975). This spread-F adaption of the model was used
subsequently to better define the sunspot cycle dependence (Singleton,
1977). The need for the model to allow for the effects which magnetic
activity have on the behaviour of the irregularities was first addressed by
Pope (1974). He proposed a modification to the model to achieve this at high
latitudes. Singleton (1978) recently indicated how the model can be further
modified so as to allow the simulation of the effect of magnetic activity on
the irregularities at the low latitudes. He also considered a further
effect, hitherto neglected in the modelling process, namely variations in
irregularity occurrence with longitude. This paper briefly outlines this
model and its derivation.
2. IRREGULARITY SIZE AND SHAPE
The early scintillation observations, which were carried out in the VHF
region, seemed to be explicable in terms of a Gaussian distribution of
irregularity size (Briggs and Parkin, 1963) which appeared to peak at about
lkm. This corresponds to the scale size to which the scintillation mechanism
is most sensitive at these frequencies, being approximately equal to the
radius of the first Fresnel zone. The reliability of the Gaussian
distribution was first thrown into doubt with the unexpected observation of
scintillation at gigahertz frequencies near the magnetic equator (Craft and
Dl - 1
Westerlund, 1972) . Subsequent in-situ measurements (Dyson et al., 1974) and
scintillation spectral studies (Singleton, 1974) have shown that the
irregularities in the F-region have a power law spectrum involving a wide
range of wavenumbers corresponding to dimensions ranging from a few metres
to tens of kilometres. Consequently, it is important that a model of
irregularity behaviour intended for universal application should both be
evaluated in terms of, and employ, a power law irregularity spectrum. A
wavenumber spectrum of monotonic power-law form involving an outer scale
size of 10km is assumed.
It is convenient to define the scintillation index S/ of a fluctuating
radio wave (whose amplitude is R) by
S4 =[[]? - (rVI /(P)2]^ (1)
In this case, it can be shown (Rufenach, 1975) that, for weak scattering
conditions, S/ is a function of the excess or deficiency of electron density
in the irregularities ^N) , the thickness of the irregular layer (^h) , the
axial ratio of the field-aligned irregularities (ex) f the angle between the
direction of propagation and the Earth's magnetic field ((/0, the outer scale
wavenumber of the irregularity spectrum (k0), the observing wavelength (X),
the distance between the observer and the irregularities (z) and the angle
of incidence of the radiation on the ionosphere (X) (vide equations (Al) to
(A6) of the Appendix).
Fremouw and Bates (1971) and Fremouw and Rino (1973) in their original
models assumed a constant value of ten for the elongation factor (ex) at all
latitudes. This figure is probably justified in the equatorial region where
values of QC in excess of 7.5 have been observed (Koster, 1963). However, at
the high latitudes (50 geomagnetic and above) values of ex in the vicinity
of 5 have been observed (Singleton, 1973). Consequently, in the present
model oc is represented by equation (A9). This gives ex = 10 for geomagnetic
latitudes (© ) from 0° to 15° , ex = 5 for 50° < 6< 90° and a smooth transition
of ex from 10 to 5 between 15 and 50° geomagnetic latitude.
3. HIGH LATITUDE MAGNETIC ACTIVITY BEHAVIOUR
Fremouw' s original model of global scintillation behaviour suffered from
the limitation that it took no account of the well established correlation
of scintillation occurrence with magnetic activity. This correlation is
negative in the equatorial region and positive at magnetic latitudes in
excess of 50°. The high latitude effect is largely due to the equator-wards
movement of the edge of the polar region of high scintillation activity (the
scintillation boundary) with increasing magnetic activity. Pope (1974)
modified Fremouw' s model so as to adequately represent these movements of
the scintillation boundary. This variant of the model will now be outlined.
The model of AN consists of four additive terms, the influence of each
being dominant in different regions of geomagnetic latitude, namely
equatorial, mid, high and auroral latitudes. These terms are functions of
some or all of the following parameters: local time (t hours), day of year
(D days), geomagnetic latitude (6 degrees), three hourly planetary magnetic
index (Kp) and the monthly smoothed Zurich sunspot number (R). In order to
retain the option of adding variations involving other variables into the
expression, a factor m has been included in each term which allows the
D1 - 2
adjustment of its magnitude. Thus the model is represented by equation (A17)
in which the subscripts e,m,a and h refer to the equatorial, middle, auroral
and high latitude regions respectively.
Using units of electrons/m> for electron density, the AN terms in
equation (A17) are
ANe = 5.5xie9(l+0.05R)[l-0.4cos|47t(D+10)/365]].
[exp|-(t/4)2|+exp|-(t-23.5)2/3.52l]exp[-(e/ee)2j (2)
and as given by equations (A23) , (A24) and (A25) of the Appendix, where 0e
= 12°, 6ra= 10° and 0 o = 32.5° .
Singleton (1977) noted that the sunspot cycle variation of AN implied by
spread-F morphology (Singleton, 1960; 1968) is inadequately modelled by the
above equations. This position can be rectified however, if sunspot number
variations of 6e , 6m ,U0 , me, mm, m^ and maas given by equations (A32),
(A35), (A34) and (A18) to (A21) inclusive, are incorporated in the model.
4. LOW LATITUDE MAGNETIC ACTIVITY BEHAVIOUR
At low latitudes increased magnetic activity tends to inhibit the
occurrence of both spread-F and scintillation (Lyon, Skinner and Wright,
1960). The nature of the correlation between scintillation index and
magnetic activity was investigated by Koster (1972) whose results for Legon
are reproduced in figure 1. Here scintillation-index observations, obtained
between July and December in a year of high sunspot activity (1969), were
first normalized so as to remove the seasonal and diurnal variations and
then plotted against the 24 hour sum of the appropriate day's Kp indices
(Sj(). Though there is considerable scatter, the diagram suggests that there
is some value of S^ below which scintillation index is independent of Sv-and
above which scintillation index decreases with increasing S . Koster
suggested a Kp sum of 30 as the boundary between these two regime^.
4.1 The model employed
Section 4.2 considers the effect of magnetic activity on spread-F
occurrence season by season. The Kp sum which separates the regime of
constant response from that of inhibition is found to vary with season. In
fact, the modelling process is best served by the three lines drawn on
figure 1, one for each of the seasons as indicated. Each of the lines is
accommodated by the scatter and indeed they suggest one plausible reason for
the scatter at the higher Sj£ values. This variation is incorporated in the
model by including in me (equation (A17)) a factor Fj^ which is an
appropriate function of Sj£ (Section 4.2).
The modified model can be tested against some scintillation index data
obtained at 45 MHz, at Accra (Koster and Wright, 1960). Diurnal
distributions obtained from this data for both the international
magnetically quiet days (circles) and disturbed days (crosses) during
sunspot maximum is shown in figure 2(a). Employing the model, together with
the published Kp and sunspot number values, to simulate the degree of
scintillation at Accra during the quiet and disturbed periods involved,
Dl - 3
X
UJ
Q
Z
o
<
.4 -
1-2 -
I.O
h- 0-8
Z
U
CO
Q 0-6
LU
_J
< 0.4
q:
2- 0.2
S. SOLSTICE
EQUINOX
N. SOLSTICE
* 1 ^^f- -#••••♦ %
12
■ ■
48
54
6C
KpSUM
Fig.l: Normalized scintillation index as a function of Kp sum.
gives the diurnal curves shown as full and broken lines respectively in
figure 2(a). The success of the modified model in predicting the levels of
scintillation activity under magnetic quiet and disturbed conditions is
obvious .
Fremouw and Rino employed an equatorial diurnal factor of the form
(equation (2))
F = exp[-(t/4)2]+ exp[-|(t-23.5)/3.5]2]
a
(3)
However, in order to obtain a good fit throughout the night between the
predicted curves and the experimental points in figure 2(a), this diurnal
factor had to be modified to be
Fd = exp[-(t/3)2l+ exp[- |(t-22)/7i9]
(4)
Koster and Wright (1960) also carried out an analysis using spread-F
occurrence data obtained at Ibadan which was similar to that described above
for their Accra scintillation data. The resulting diurnal distributions are
shown in figure 2(b). In order to simulate this data, it is necessary to
employ the spread-F adaption of the scintillation model (Singleton, 1975).
D1 - k
t — I r
T 1 r
22 OO 02
LOCAL TME CHRS)
Fig. 2: Magnetically quiet and disturbed levels (circles and
respectively) of scintillation observed at Accra and
occurrence at Ibadan at sunspot maximum.
crosses
spread-F
This adaption employs an empirical model of the maximum electron density of
the F layer N (Chiu, 1975) in combination with AN to simulate both the mean
spread in critical frequency Af (equation (A8)) and the percentage
occurrence of spread F P (equation (A7)). This procedure (Briggs, 1964)
removes the apparent modulation of the occurrence of irregularities by the
strength of the background layer when spread F is used as an indicator of
D1
irregularity presence (Singleton, 1962). This is the same modulation which
results in the frequently reported anticorrelation of the occurrence of
spread F and scintillations. The curves for magnetically quiet and
disturbed days resulting from such a simulation of the Ibadan data are shown
as the full and broken lines respectively in figure 2(b).
The scintillation modelling process depends on a simulation of the
product AN(Ah)2 , while the spread-F adaption of the model does not involve
Ah. Consequently, a diurnal variation in AN implied from scintillation data
may be confused by a diurnal variation in Ah. However, this will not be the
case for diurnal variations of AN obtained from spread-F data. It has been
customary in F-region irregularity modelling to use a constant value of Ah,
namely 100km, when considering scintillation data. However, the degree of
fit between the model and the spread-F data illustrated in figure 2(b) can
only be obtained if the AN diurnal variation, based on the scintillation
data, is altered to accommodate a Ah, which, in the equatorial region, is
assumed to vary as
Ah = lo(1+t18/6) (5)
where t^o is local time in hours from 1800 LMT. Consequently, the diurnal
factor in the equatorial term of the Fremouw and Rino model of AN is
modified so that when combined with this nocturnal variation of Ah, no
change is made toAN(Ah) . In this way, the modelling of scintillation
index remains unaltered while allowing a successful modelling of spread-F
occurrence. Because of the ad hoc nature of this variation of Ah, the
possibility that it may also encompass real differences between the
irregularities responsible for spread F and scintillations cannot be
di smi ssed .
4.2 Choice of the seasonal magnetic factors
Figure 3 shows some further occurrence results for equatorial spread F
(Lyon et al. 1960). Here sunspot maximum data were used to produce diurnal
percentage occurrence diagrams for magnetic quiet days (circles) and
disturbed days (crosses). The data were obtained at several observing
stations in the Afro-Indian zone (20°W to 80° E longitude), while the curves
simulated with the modified model are appropriate to Ibadan (3.9°E).
Two changes to the seasonal dependence of the Fremouw and Rino model were
found to be necessary in order to obtain the fit between the simulated
diurnal variations and the experimental variations illustrated in figure 3.
The first involves adopting the magnetic inhibition relationships already
mooted in Section 4.1. These are given by equations (A28), (A29) and (A30)
where F~ is 1.05, B^- is 17 in the southern solstice, 19 in the equinox and
27 the northern solstice and where (Bt/- + Fq/A^ ) is 45. The second
modification involves the overall seasonal variation in AN. Fremouw and
Rino model the seasonal variation as a simple sinusoidal semi-annual
variation peaking in the equinoxes (equation (2)). However, as Koster (1972)
points out, there is also a considerable annual variation in scintillation
index as observed at Legon and such a variation has been included in the
modified model. The seasonal term in equation (2), namely
Fo = [l -0.4 cosi47i(D+10)/365] ] (6)
s
was replaced by
DI - 6
Fa =[l -0.36cos{4<D+10)/365j+0.25cos|27t(D+10)/365|]
(7)
IOO
uj (B) l8
&IOO
50-
O
CO
o
o
«
0
^^ N. Solstice
f
7
X
X
X
/ ' *
/ ' x
X
"■ ■*■» x\
"NX a
■A* ,
<
1 '
1 1 1 -Si 1 — .
18 20 22 OO 02
LOCAL TIMECHRSJ
04
06
Fig. 3: Magnetically quiet and disturbed levels (circles and crosses
respectively) of spread-F occurrence at Ibadan in each of the
seasons at sunspot maximum.
4.3 Sunspot cycle effect
The investigation of scintillation at Accra and spread-F at Ibadan by
Koster and Wright (1960), besides giving the sunspot maximum results of
figure 2, also presents similar results under sunspot minimum conditions
(figure 4). Only two changes are found to be necessary to produce the
illustrated degree of fit between the simulation and experiment. The first
involves the diurnal distribution factor which is required to take the form
Fd = exp[-(t/3)4]+ exp[-|(t-21.5)/6]2]
(8)
The second modification involves the variation of the thickness of the
disturbed region through the night. This is required to be of the form
(9)
Ah = 10 (1+tl8/l8)
Equations (5) and (9) can be generalized to give
Ah = 10 (1+tl8/Tl8) (10)
Also, the diurnal function (Fd) can be generalized to give equation (A26),
the variation from sunspot maximum to minimum conditions being accounted for
by employing t ,rm, q and T[q as given in equations (A38) to (A4l).
D1
(B) O
22 OO 02
LOCAL TIME CHRS.)
Fig. 4: Magnetically quiet and disturbed levels (circles and crosses
respectively) of scintillation observed at Accra and spread-F
occurrence at Ibadan at sunspot minimum.
5. THE LONGITUDE DEPENDENCE AT LOW LATITUDE
Lyon et al. (1960) analysed spread-F data obtained during the I.G.Y. at
fifty-seven equatorial stations. They divided the stations into three
geographic longitude zones, the American zone (longitudes 45 W to 85 W) , the
D1 - 0
African zone (longitudes 20°W to 80°E) and the Asian zone (100°E to 160°E)
and produced magnetic latitude variations of occurrence, season by season,
for each zone. Their data points are reproduced in figure 5. The filled
circles represent the observed occurrence situation during magnetically
quiet days and the crosses correspondingly for magnetically disturbed days.
The curves drawn on figure 5 are not those drawn by Lyon et al. and should
be neglected for the moment.
Northern Sofelicc
Equnc*
Southern Sobtce
r
i pojjos jo »3ujj J15DQ Jteiujiutf
D1 - 9
As Lyon et al. point out, the points on figure 5 show that there are
longitudinal and seasonal variations in (a) the overall occurrence of spread
F, (b) the extent of the occurrence reduction accompanying magnetic
activity, (c) the width of the equatorial region of enhanced spread-F
activity, and (d) the position of the region with respect to either the
magnetic or geographic equator. These variations will now be included in
the model.
It should be noted that the results for the African zone (figures
5(b),(e) and (h)) were derived from the same data used to produce the
diurnal variations of figure 3. As these diurnal variations have been
accommodated by the model already (Section 4.2), the model as described
above should predict the occurrence levels of the peaks of the latitude
distributions for both quiet and disturbed days in figures 5(b), (e) and
(h) . This is found to be the case. Of course the model, at this point, also
predicts similar levels for all other longitudes (£) which is obviously
erroneous.
5.1 Quiet-day occurrence
In order to establish a basis on which to model the longitudinal-seasonal
variation (figure 5), the seasonal factor (equation (7)) was replaced in
equation (2) by a particular value which will be called a peak occurrence
factor (Fa) . For each of the nine combinations of season and longitude
displayed in figure 5, peak occurrence factors were chosen so as to cause
the model's prediction of spread-F occurrence to fit the observed quiet day
occurrence peaks. These calculations employed the values of Kp and sunspot
number observed during the appropriate periods. As expected in the African
zone, the peak occurrence factors are as given by equation (7).
Mathematical expressions were found which describe the seasonal and
longitudinal variations of the peak occurrence factors. These are equations
(A27), (A42), (A43) and (A44) .
5.2 Critical value of Kp sum
From figure 5 it is obvious that the extent of the reduction in spread-F
occurrence accompanying increased magnetic activity varies with both season
and longitude. In Section 4.1 it was suggested that the occurrence reduction
occurs when the 24-hour Kp sum surpasses some critical value. Variation of
this critical value with season and longitude therefore, provides the basis
for a model of the magnetic activity effect. The critical Kp sum (Bk) for
each of the combinations of longitude and season represented in figure 5 can
be determined by forcing the model to reproduce the disturbed day peak
occurrences. A set of mathematical expressions were derived which describe
the seasonal and longitudinal variations of the critical Kp sums (Bj^) • These
are equations (A45), (A52) , (A53) and (A54) .
5.3 Incremental width
Fremouw's original model of AN assumed that the equatorial region of
high activity was centred on the geomagnetic equator and fell off with
latitude according to exp j -(9/6e)^j where 6e is a constant "width" of 12°.
Examination of figure 5 suggests this is an approximation with regard to
both the position of the peak and its width. While the question of width
D1 - 10
will be examined in this section and that of peak position in the next
section, in practice these quantities were necessarily modelled in concert.
A value of 6e was found which, when subtituted for 6 e in equation (2)
allowed the model to adequately represent the spread-F data for each of the
seasons and longitudes represented in figure 5. The corresponding
incremental widths (A6e = Gg -6e) were found to be adequately modelled by
equations (A33), (A49), (A50) and (A51).
5.4 Latitude of the occurrence peak
As indicated in Section 5.3, the peak of irregularity activity in the
equatorial region is not always on the geomagnetic equator and the model
should allow for the deviations. This, together with the variations in
width just discussed, is taken into account by ^replacing the exp[-(0/9er5
term in equation (2) by exp[ - i(9+6d)/(^ +^6^] ]. Deviations (©cj) were
found for each of the seasons and longitudes represented in figure 5. These
were modelled by equations (A31), (A46) , (A47) and (A48) .
5.5 Total longitude dependence
When the four longitude variations discussed above are included in the
model, which is also supplied with the observed values of Kp and sunspot
number, the resulting latitude distributions for each of the seasons and
longitudes of figure 5 are as shown by the curves on that figure. The full-
line curves represent the quiet day situation, while the broken lines are
for disturbed days. As expected, the model provides a good simulation of
the experimental situation.
6. BLACKOUT FACTOR
At latitudes in excess of a critical value 6C (about 70° geomagnetic) ,
the adaption of the AN model to simulate spread-F occurrence requires the
inclusion of a blackout factor (Singleton, 1975). This factor, which is
applied directly to the occurrence probability predicted by equation (A7),
is believed to be due predominantly to the effect of polar blackout on an
ionosonde's ability to detect spread F. The blackout factor (B) is given in
equations (All) to (A16) inclusive (SLngleton, 1977).
7. MODEL VALIDATION
The major modifications made to the model affect the equatorial region.
Consequently, it is essential to test it against independent data obtained
in this region. This has been done successfully with regard to the
simulation of both scintillation and spread-F activity (Singleton, 1978).
8. CONCLUSION
The model has been developed considerably by incorporating in it
information from a number of published data bases other than those used
originally by Fremouw and his co-workers. Scintillation data has been
01 - 11
supplemented by spread-F data in those areas of the modelling process in
which the scintillation data was found to be inadequate. The model's
validity has been demonstrated by testing it against a number of other data
bases. Consequently, the improved model can be used with confidence as a
simulation technique in engineering studies of propagation configurations
affected by F-region irregularities.
REFERENCES
Briggs, B.H. (1964): Observatios of Radio Star Scintillations and Spread-F
Echoes Over a Solar Cycle, J. Atmos. Terr. Phys., 26:1.
Briggs, B.H. and J. A. Parkin (1963): On the Variation of Radio Star and
Satellite Scintillation with Zenith Angle. J. Atmos. Terr. Phys.,
25:339.
Chiu, G.J. (1975): An Improved Phenomenological Model of Ionospheric
Density. J. Atmos. Terr. Phys. , 37:1563.
Craft, H.D., and L.H. Westerlund (1972): Scintillation at 4 and 6 GHz Caused
by the Ionosphere, AIAA Paper No. 72-179, American Inst. of
Aeronautics and Astronautics Library, 150 Third Ave., New York.
Dyson, P.L. , J. P. McClure, and W.B. Hanson (1974): In-Situ Measurements of
the Spectral Characteristics of F-Region Ionospheric Irregularities, J.
Geophys . Res . , 79:1495.
Fremouw, E.J.,and J.F. Bates (1971): Worldwide Behaviour of Average VHF-UHF
Scintillation, Radio Sci. , 6:863.
Fremouw, E.J., and C.L. Rino (1973): An Empirical Model for Average F-layer
Scintillation at VHF-UHF, Radio Sci. , 8:213.
Koster, J.R. , and R.W. Wright (1960): Scintillation, Spread F and
Transequatorial Scatter, J. Geophys . Res. , 65:2303.
Koster, J.R. (1963): Some Measurements of the Irregularities Giving Rise to
Radio Star Scintillations at the Equator, J. Geophys . Res . , 68:2579.
Koster, J.R. (1972): Equatorial Scintillation, Planet. Space Sci. , 20:1999.
Lyon, A.J., M.J. Skinner, and R.W.H. Wright (1960): The Belt of Equatorial
Spread-F, J. Atmos. Terr. Phys. , 19:145.
Pope, J.H. (1974): High Latitude Ionospheric Irregularity Model, Radio Sci. ,
9:675.
Rufenach, C.L. (1975): Ionospheric Scintillation by a Random Phase Screen:
Spectral Approach, Radio Sci. , 10:155.
Singleton, D.G. (1960): The Geomorpnology of Spread F, J. Geophys. Res.,
65:3615.
D1 - 12
Singleton, D.G. (1962): Spread F and the Perturbations of the Maximum
Electron Density of the F-Layer, Aust. J. Physics. , 15:262.
Singleton, D.G. (1968): The Morphology of Spread-F Occurrence Over Half a
Sunspot Cycle, J. Geophys . Res . , 73:295.
Singleton, D.G. (1973): The Dependence of High-Latitude Ionospheric
Scintillations on Zenith Angle and Azimuth, J. Atmos. Terr. Phys . ,
35:2253.
Singleton, D.G. (1974): Power Spectra of Ionospheric Scintillation, J.
Atmos. Terr. Phys. , 36:133.
Singleton, D.G. (1975): An Empirical Model of Global Spread-F Occurrence, J.
Atmos. Terr. Phys. , 37:1535. ~
Singleton, D.G. (1977): The Reconciliation of an F-Region Irregularity Model
with Sunspot Cycle Variations in Spread-F Occurrence, Radio Sci. ,
12:107.
Singleton, D.G. (1978): An Improved Ionospheric Irregularity Model,
ERL-46-TR, Electronics Res. Lab., Dep.of Def . , Australia.
APPENDIX: THE PROPOSED MODEL
The following is a concise statement of the model. The scintillation
index S4 is given by
S4 = 2Y<PoFf(/3) (Al)
where
^0 = [^T(r^)AN(Aha),i-/2T(/3k0)7](secx)i (A2)
F = J l-exp(-M) 1 * (A3)
f(/5) = (3/? 4+2/32 +3) /[ 2(2)^1 (A4)
fl = (Xz/27i)k02 (A5)
(3 2= cos2ip +a2sin2<A (A6)
The probability of occurrence of spread-F is given by
ft= 50 [l-erfK2(Afc/Afo-l)n (A7)
where
A fig = ionosonde frequency resolution (typically 0.1MHz),
Af0 = 8.98xl0"6 j(N +AN)^ -*£ 1 (A8)
The following parametric variations constitute the model. The elongation
factor a is given by
a = 10-2. 5[l + erf [(0-35)/lO j] (A9)
The effective thickness Ah is given by
D1 - 13
Ah = 10 (1+tl8Al8) (A10)
The blackout factor B is given by
B = 1 + A[cos[27i(t-r)/24J - l]
+ C[cos[47<t-r)/24]-l] iexp|-(0-0c)2/0p2l (All)
where -'
A = (0.l4-0.000275R)[l-(0. 7857-0. 000987R)cos[2x(D+10)/365]
-(0. 2143-0. 000777R)cos[4^(D+10)/365] ] (A12)
C = (0. 025+0. 0003R)[ l + (2-0.01R)cos[27t(D+10)/365j
+ (1-0.01R)cos[4ti(D+10)/365]] (A13)
t = (2.75+0.005R)[l+0.0073Rcos[2^(D+10)/365i
+ (0. 091+0. 0032R)cos |47t(D+10)/365] ] (A14)
0C = (66. 25-0. 0063R)[ l+(0. 0377-0. 0096R)cos[27^(D+10)/365]
+(0. 0189-0. 00048R)cos| 47i(D+10)/365l] (A15)
6p = (229. 5+0. 019R)[l+(0. 6144-0. 00021R)cos[27t(D+10)/365J
-(0. 307-0. 00011R)cos[4ti(D+10)/365] ] (A16)
The F-layer peak electron density N is given by a model due to Chiu(1975)
and the incremental electron density in the irregularities AN is given by:
AN = meANe(R,D,t,e,2,SK)+mi^Nm(t,e)
+mjANh(t,Kp, 0 )+maANa(t,R,0) (A17)
where
me = 3.2 - 0.011R (A18)
mm = 8.6 - 0.032R (A19)
mh = 11.0 - 0.041R (A20)
ma = 15.0 - 0.066R (A21)
ANe = 5.5xlO9FdFsFK(l+O.O5R)expl-(0 + 0d)2/(0e+A0e )2j (A22)
ANm = 6.0x10 il+0.4cos(7it/12)lexp[ -(0-0o) /©m j (A23)
ANh = 2.7xl0^1+erf |(0-0b)/0h j] (A24)
ANa = 5.OxlO7Rexp[-|0-7O+2cos(-Kt/12)] 2/[o.03RJ2] (A25)
Fd = l(jexp[-(t/3)4]+exp[-[(t-tm)/Tmj ^/w^^Q^S^2 (A26)
Fg = PJ 1 + Scos2 -Hcos(22 )] (A27)
FK = Fc for0<SK<BK (A28)
D1 - 1A
^-A^-F^) for Bj^SjfCBjj+FQ/Ag) (A29)
= 0 for S^ (%+Fc/Ag) (A30)
©d = V[l-AVcosJ27i(D+10)/365J-SVcos[47i(D+10)/365J ] (A31)
©e = -11.5R + 34.5 (A32)
A6e = T[l-ATcos|2^(D+10)/365|-STcos|47i(D+10)/365] ] (A33)
©o = -0.085R + 49 (A34)
6m = 6.75 + 0.0l65R-(3.25-0.0l65R)cos(27tD/365) (A35)
6b = 68-[D.75+0.25cosi'K(t-21)/12l ]Kp-7.5cosU(t-21)/12i (A36)
8h = 7 - 3cos[r,(t-21)/12J (A37)
^ = 21.5 +0.0025R (A38)
rm = 6.0 + 0.005R (A39)
q = 2.0 + 0.035R (A40)
T = 18.0 - 0.06R (A41)
I o
P = 0.628[l+0.170cos|27i(D+10)/365i-0.402cos[4^(D+10)/365|] (A42)
S = -0.08 [l-1.375cos[27t(D+10)/365i-1.25cos[47t(D+10)/365i 1 (A43)
H = 0.5[l+0.08cosb7i(D+10)/365l+0.06cosJ4tt(D+10)/365] ] (A44)
B = K[l-AKcos[2^(D+10)/365]-SKcos[4^(D+10)/365]] (A45)
V = -0.508-1.74cosS2 +3.30sinS2 (A46)
SV = (-0. 873-1. 13cosS2+3.47sinS2)/V-l (A47)
AV = (-2.721-5.78cos£ +5.0 sin&)/V (A48)
T = 4.86+3.l4cosS -0.994sin2 (A49)
ST = (6.l6+6.84cos 2-3.72sin2 )/T-l (A50)
AT = (1.98-0.98cosS2 -1.75sinS2 )/T (A51)
K = 24.6l+6.88cos2 -6.89sin£ (A52)
SK = (22.57+8.43cos2 -6.87sinS2)/K-l (A53)
AK = (-1.09+2.09cosS2 +5.72sinS2)/K (A54)
Quantities not specified above are defined in the main text.
01 - 15
PREDICTING TRANS IONOSPHERIC PROPAGATION CONDITIONS
D. G. Singleton
Defence Science and Technology Organization,
Electronics Research Laboratory,
Salisbury, S.A. , Australia.
A method is developed for predicting propagation conditions on
transionospheric circuits. The method combines a realistic model
of F-region irregularity behaviour with thin screen scintillation
theory in order to simulate both the mean scintillation index and
the probability of the signal falling below a nominated level.
Consideration is given to the application of the prediction method
to transionospheric circuits terminated by a synchronous satellite
at 176. 5°E (e.g. MARISAT II) and by points on the Earth's surface
within an area bounded in latitude by 30 N and 65 S and in
longitude by 75°E and 270°E. A partial validation of the model is
provided by a comparison of its prediction of scintillation index
with observational data obtained at Manus Island.
1. INTRODUCTION
The most serious cause of disruption to space-Earth radio communications
is of natural origin. It results from the phenomenon known as
scintillation. In this phenomenon the steady signal at the receiver is
replaced by one which is fluctuating in amplitude, phase and apparent
direction of arrival. Early investigation (Booker, 1958) established that
the signal fluctuations were introduced as the result of the passage of the
radio wave through an irregular ionosphere. In particular, electron-density
irregularities in the F-layer of the ionosphere are now known to be the
prime cause of the fluctuations.
In the last two decades considerable effort has been expended in
establishing the properties of the electron density irregularities in the F-
layer (Getmantsev and Eroukhimov, 1969). Sufficient is now known so as to
allow the behaviour of the irregularities to be modelled in an empirical
way. The early models (Fremouw and Bates, 1971; Fremouw and Rino, 1973) were
based on a limited amount of scintillation data and neglected such important
aspects as the dependence of the irregularity occurrence on magnetic
activity and longitude. Recently, the ability to use spread-F data obtained
from ionograms (Singleton, 1975) has added another dimension to the
modelling process (Singleton, 1977 ; 1978) and more realistic models of the
behaviour of the irregularities now exist (Singleton, 1978).
The next section outlines a model by means of which the nature and
behaviour of the F-region irregularities can be simulated. It is shown that
D1 - 16
this modei, coupled with the thin-screen theory of scintillation, leads to a
means of predicting propagation conditions on transionospheric circuits. A
partial validation of the model is carried out by comparison of its
prediction of scintillation index at Manus Island with data obtained there.
Section 3 then examines the application of the prediction scheme to circuits
operating between a synchronous satellite at 176.5 E and the Earth's
surface. Particular attention is paid to variations in latitude, longitude,
day-of-year, time-of-day and the effects of changes in magnetic activity and
sunspot number. The significence of these predictions is discussed in
Section 4.
2. THE MODEL
2.1 The propagation mechanism
If a plane radio wave is incident on a smooth horizontally stratified
ionosphere it emerges as a plane wave. On the other hand, if there are
irregularities of electron density embedded in the F layer, neighbouring
parts of the wave traverse regions of different refractive index and the
emerging wave wavefront is distorted due to the correspondingly different
phase propagation times. As the wave propagates away from the irregular
layer, the phase distortions give rise to amplitude fluctuations (Briggs and
Parkin, 1963). That is, a diffraction pattern is developed. The depth of the
amplitude fluctuations in this pattern increases with increasing distance
from the irregular layer up to a limiting value, which persists as the wave
travels on further. Passage of the irregularities overhead and/or movement
of the source causes the diffraction pattern to move and hence a fluctuating
signal is presented to a point receiver.
In order to quantify the fluctuations in the amplitude (R) of the
scintillating signal, a quantity called the scintillation index (S) is
defined as follows.
S = [[R*- (P7)2j/ (p7)2F
By considering first the properities of the wavefront on emergence from the
irregular region in terms of the properites of the ionization density
irregularities, and then dealing with the subsequent diffraction problem, it
is possible to show (Briggs and Parkin, 1963; Singleton, 1970) that
S = fiX,(AN2)^Ah,K0,p,a,i,^,z1,z2] (1)
where A = transmitting wavelength,
(AN )*= the rms deviation of electron density in the irregularities.
^h = thickness of the irregular layer,
Ko= outer-scale wavenumber of the irregularity spectrum,
p = spectral index of the irregularity spatial spectrum,
ex = irregularity elongation factor along the Earth's magnetic field,
i = angle of incidence of the wave on the ionosphere,
D1 - 17
y = angle between the direction of propagation and the Earth's
magnetic field,
z ] = distance of the receiver from the irregularities and
Z2= distance of the transmitter from the irregularities.
This expression is valid if the deviations of phase across the emergent
wavefront are less than one radian. For phase deviations greater than this,
a strong scattering approximation must be used and values of S greater than
one may be encountered. This condition is referred to as saturation
(Singleton, 1970).
The variables X, i , <p , Zy and z p in the function f (equation (1)) are
directly dependent on the transmitter, ionosphere and receiver configuration
and can be easily determined in any particular case. On the other hand, the
quantities (AN ^) *, Ah,KQ,p,a describe the nature of the irregular region.
2.2 The nature of the irregularities
The gross features of the nature and behaviour of ionospheric
irregularities have been determined by means of innumerable studies
involving scintillations (Getmantsev and Eroukhimov, 1969), spread F
(Herman, 1966) and in-situ measurements (Basu et al., 1976). Initially
Fremouw and Bates (1971) and Fremouw and Rino (1973) summarized those
properties of F-region irregularities, which can be determined by means of
the scintillation phenomenon, in terms of a set of empirical equations.
These expressed (AN2)"? as a function of year, day-of-year, time-of-day,
latitude and running average sunspot number (RASN) . By employing spread-F
data (Herman, 1966), which is more plentiful than scintillation data,
Singleton (1975; 1977) was able to further define the role of the sunspot
cycle in these equations, as well as include effects due to changing
magnetic activity and longitude. Temporal variations of Ah and latitude
variations of K0 and Ot were also included in this model. The result
(Singleton, 1978) is a set of empirical relations which give, in analytic
form, a realistic expression of the nature of the irregularities responsible
for scintillation on transionospheric circuits.
2.3 Predicting scintillation index
By combining the results of the scintillation theory (equation (1)) with
the model of irregularity behaviour described in Section 2.2, it is possible
to give analytic expression to the manner in which the scintillation index,
observed on any transionospheric circuit, varies with such parameters as the
positions of the terminals of the circuit, year, day-of-year, hour-of-day,
magnetic activity, sunspot number and operating frequency. Computer
programs have been written which embody this analytic formulation and which
thereby allow the prediction of scintillation index for various
transionospheric propagation circuits.
Figure 1 shows an output from one such program. Here a transmitting
satellite at synchronous height over the equator at 176.5° E is considered.
Contours of equal scintillation index are drawn for reception points on a
D1 - 18
m
<x
If)
cc
oc
ID
ED
(J
to
cc
>- UJ
_l OQ
0_ 3C
—> 3
OCR06
OQ-qt
00 '.9
N
n
(-030) 30011101 "0030
00 '9,- 00 '81,- 00 'OE,- 00 -gr)-
oo 'ny-
00'99-
1!
4->
•H
4->
O
00
o
oj
60
<n
x
CI
CI
o
•H
4-1
A3
d
•H
U
M
ex
O E
aj
^ 3
d P
o -H
P oo
c a
o o
U .-I
oo
•H
00*06
00*8t
00'81- OO'OE- OO'eh-
)3Q) 30011101 '0030
OO'HS-
00-99-
D1 - 19
map of the area between 30° N and 66°S geographic latitude and 75° to 270°E
geographic longitude. Note the contours are limited necessarily to that
part of the Earth's surface in view of the satellite (i.e. within the
horizon curves on the figure) . This particular diagram represents the
predicted behaviour of all possible transionospheric circuits operating on
day 80 of 1978 at 1200 hours UT. A frequency of 257 MHz, which corresponds
to the down-link frequency of MARISAT II, was employed in the calculations.
The expected running average sunspot number (RASN) at this time was 45 and
the sum of the Kp figures for the day (SKp) was taken as 5. Local time is
indicated across the top of the diagram.
Two regions of high scintillation activity are indicated in figure 1: one
along the geomagnetic equator and a second at high latitudes. There is only
slight activity in the middle latitudes. Note that at this time the
scintillation index becomes saturated rather rapidly at the high geomagnetic
latitudes, while saturation is limited to an area over the mid-Pacific Ocean
in the equatorial region. It should be recalled that the figure is a
prediction of the mean scintillation index. No indication is given as to
the extent of the scatter individual observations of scintillation index
might have about the mean at this time.
Equation (1) shows that the scintillation index depends on the distance
of the receiver from the irregularities (z -j ) and the distance of the
transmitter from the irregularities (zj. However, the nature of this
dependence is such that, in any particular case, the interchange of z-| and
Z2 does not alter the value of S. Thus for a two way communication system,
the scintillation index expected on the up-link should be the same as that
predicted for the down-link.
2.4 Model Validation
In order to completely validate the model throughout the area shown in
figure 1, observations at a number of points would be required. At present,
only MARISAT data from Manus Island (147.37°E, 2.04°S) is available, though
other observations are planned. This site is strategically placed however,
being just inside the equatorial region of high activity. A favourable
comparison of the model's predictions with data from this site would add
considerable credence to the usefulness of the model.
Digitized signal-strength data from Manus Is. has been reduced to provide
half-hourly S values during the period August to November 1976. For each of
these months diurnal distributions of scintillation activity have been
produced and are given in figure 2. Each plot shows the diurnal variation of
each of the following: the mean scintillation index (full line curve), the
range of observed values of S (vertical full lines) and an index value one
standard deviation of the hourly distribution of S from the mean index for
that hour (points on the vertical lines).
The model was employed to provide a detailed prediction of scintallation
activity during each of these months. Actual values of sunspot number and Kp
were employed to predict the scintillation index for each hour of each day
and this data was then used to form diurnal distributions of mean index.
These diurnal distributions are shown as the broken-line curves on figure 2.
Figue 2 indicates that the model provides a good simulation of the actual
observations, the predicted mean index generally being within one standard
deviation of the observed mean index.
D1 - 20
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D1 - 21
2.5 Predicting disruption probability
Scintillation index proves to be a convenient measure of scintillation
activity when the observation of scintillation is used as a technique for
studying ionospheric irregularities. However, in the engineering of
communication circuits employing transionospheric propagation, a more system
oriented measure is needed, such as the probability of communication being
lost due to scintillation effects. For most communication systems, the
"outage" probability can be defined quantitatively as the probability of the
signal level falling below some designated value. This threshold signal
level is usually the noise level and, in this case, the maximum allowable
fade margin is equal to the signal-to-noise ratio in dB. Hereafter, the
probability of the signal falling below the fade margin will be called the
disruption probability and its relationship to the scintillation index will
now be examined.
Whitney et al. (1972) demonstrated that the probability distribution of
signal amplitude (R) for a scintillating signal is closely represented by
the Nakagami m distribution (Nakagami, 1960). This is
p(R) = 2m qR2m-1 exp(-mR2/P)
T(m) (R?) 2
where m can be shown to be 1/S . Defining signal level X as
X = 10 log10(R2/R~2)
it follows from the Nakagami distribution that the probability of the signal
level falling below some specified level X0 is
Xo
p(Xo) = f 2m m exp[m[2X/M - exp(2X/M)l ]dX (2)
J MT(m)
— oo
where M = 20 log^e. Thus, if Xq is the threshold of the fade margin, then
P(X0) corresponds to the disruption probability. •
The integral in equation (2) is readily evaluated and since S = m~^, it
allows predictions of mean scintillation index to be converted to
predictions of disruption probability. Figure 3 is the disruption-
probability prediction corresponding to the scintillation-index prediction
of figure 1. Here disruption probability (expressed as a percentage) for a
fade margin of -6dB is plotted as a series of contours on the same map as
that used for figure 1.
As expected, figure 3 has similar characteristics to figure 1. The areas
affected by scintillation appear to be slightly reduced in terms of signal
level probability as compared with the scintillation index indication. This
merely reflects the fact that, under weak scintillation conditions, the
probability of 6dB fades is low. Note also that the scintillation index to
disruption probability conversion is only possible where the scintillation
index ^.1. The model is unable to comment on disruption probability where
the scintillation index is saturated, except to say that the disruption
probability in the saturated region will be higher than the disruption
probability just outside this region. Thus at high latitudes immediately
D1 - 22
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23
south of Australia, the disruption probability rapidly increases to values
in excess of the saturation value which is itself in excess of 15%.
From the above it will be seen that equation (2), coupled with equation
(1) and the model of ionospheric irregularities discussed in Section 2.2,
provides the engineer designing a transionospheric propagation circuit with
a means of determining the fading margins necessary to overcome
scintillation effects under various conditions. In order to evaluate the
performance of a proposed system, disruption probabilities for various
critical signal levels are usually needed as a function of latitude,
longitude, time-of-day, season, level of magnetic activity and phase of the
sunspot cycle. The next section illustrates such a performance evaluation
for MARISAT II.
3. THE MODEL'S PREDICTIONS
3.1 Variations with latitude and longitude
Consider the case of a communications satellite at synchronous height
over the equator at 176. 5° E with up-link and down-link frequencies near 257
MHz. If the fade margin allowed is 6dB, then the instantaneous picture at
1600 hours UT of the likelihood of disruption to both the down- and up-link
transmissions over a wide geographical area is as shown in figure 3. As
indicated earlier, the likelihood of disruption to these circuits is limited
to those terminating in the equatorial and high latitude regions. This
style of presentation will be used in the following sections to examine how
the geographic distribution of circuit performance varies with time-of-day,
season, magnetic activity, sunspot cycle and critical level.
3.2 Diurnal variations
The diurnal development of the equatorial and high latitude areas of
scintillation activity can be gauged by a comparison of figures 3 and 4. In
figure 4(a) the western half of the diagram is experiencing late morning,
noon and afternoon conditions for which there is little scintillation
activity in either the equatorial or high latitude regions. Activity in the
equatorial region rapidly builds up on the satellite's eastern horizon
however, where late evening conditions prevail.
The instantaneous picture eight hours later at 1200 hours UT (figure 3)
shows that the equatorial region of high activity has moved out over the
mid-Pacific Ocean and circuit disruption at the 6dB level is experienced
over a wide area. At the high latitudes during the eight hours between the
instantaneous pictures of figures 4(a) and 3, the affected region moves
equator-wards and ♦"he maximum disruption probability increases from 4% to
something in excess of 15%. By 1800 hours UT (figure 4(b)), the equatorial
activity has retreated into the western horizon of the satellite's field of
view and the high latitude activity has started to fall back towards the
South Pole. Thus the high activity in the equatorial region moves along the
geomagnetic equator being roughly centred on local midnight.
D1 - 24
PROB LESS -6DB 1978 DAT 80 400Z 257MHZ RflSN 45 SKP 5
° LOCAL TIME IHRS) g
T> 00 10.00 II. CO 12.00 13.00 1H.00 IS. 00 16.00 17.00 18.00 19.00 20.00 21.00 22.00
CONTOURS PRE 0/0
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NUMBERS BT
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'75.00 9b. 00 105. 00 120.00 135.00 150.00 165.00 180.00 195.00 2'lO.OQ 225.00 alio. 00 255.00 27d . 00
C-EOG. LONGITUDE IDEG. ERST)
CA3
PROB LESS -6DB 1978 DAY 80 1800Z 257MHZ RflSN 45 SKP 5
° LOCRL TIME IHRS) g
23.00 2M.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 32.00 33.00 34.00 35.00 36.00
B
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00 135.00 ISO. 00 lbs. 00 180.00 195.00 ?'l0.00 225.00 iUoToO 255.00 276.00
GEOG. LONGITUDE (DEG. ERST)
Fig. 4: An illustration of the diurnal development of the equatorial and
high latitude disturbed regions.
D1 - 25
3.3 Seasonal variations
In the equatorial region of high scintillation activity, the likelihood
of disturbance to a transionospheric circuit is greatest in the equinoxes
(figure 3). In the solstice periods it is found that, there is little
likelihood of circuit disruption in the equatorial region.
In the high latitude region of high scintillation activity there is
little seasonal effect.
3.4 Magnetic activity variations
Magnetic activity affects the low and high latitude regions of high
activity differently. The measure of the degree of magnetic activity used
here is the sum (SKp) of the eight three-hourly planetary K figures for a
day. In figure 3 SKp is 5. This is increased to 30 and 50 in figures 5(a)
and (b) respectively.
An increase of SKp from 5 to about 20 affects the equatorial activity
little. However, at the high latitudes, this SKp increase causes the active
region to move some 2° towards the equator. Increasing SKp from 20 to 30
takes the high latitude region only about 1° nearer the equator but causes a
marked decrease in equatorial activity (figure 5(a)). A further increase of
SKp by 10 (figure 5(b)) sees the equatorial activity disappear altogether,
while there is a further slight movement of the high latitude active region
towards the equator.
It is clear that magnetic activity ranks with geographic position, time-
of-day and season as a factor which needs to be taken into account in
determining the usefulness of a transionospheric circuit.
3.5 Sunspot cycle variation
Figures 3 and 6 illustrate the effect of the changing sunspot cycle on
the disruption probability under equinoxial conditions. The disturbed
equatorial region not only expands in size with increasing sunspot number
but also increases in intensity. Increasing the sunspot number (RASN) from
10 to 40 (figures 6(a) and 3) causes the peak disruption probability to
increase from 4% to something in excess of 15%.
In the present sunspot cycle these values of RASN will be exceeded by mid
1978 and values well in excess of 100 will be encountered by 1980. Figure
6(b) gives an indication of the severe conditions which can be expected at
that time. The whole equatorial (magnetic) region of the area of interest
will be subject to circuit dislocations for much more than 15% of the time.
At the high latitudes the disturbed region appears to be altered little
by increasing values of sunspot number when these are moderate values
(figures 3 and 6(a)). At the higher sunspot numbers (figure 6(b)) there
appears to be a slight contraction of the disturbed region towards the South
Pole.
D1 - 26
PROB LESS -6DB 1978 DAT 80 1200Z 257MHZ RflSN 45 SKP 30
LOCAL TIME (HRS) °
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GEOG. LONGITUDE (DEG. EAST)
8
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Fig. 5: The effect of magnetic activity on the disruption probability in
the disturbed regions.
D1 - 27
PROB LESS -6DB 1978 DAT 80 1200Z 257MHZ RflSN 10 SKP 5
LOCPL TIME IHRS) g
47.00 10.00 19.00 20.00 21.00 22.00 23.00 2M.00 2S.00 26.00 27.00 28.00 29.00 30 CO
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GEOG. LONGITUDE (DEG. EAST)
PROB LESS -6DB 1978 DRY 80 1200Z 257MHZ RflSN 180 SKP 5
LOCAL TIME (HRS) S
,47.00 18.00 19.00 20.00 21.00 22.00 23.00 2U.00 2S.00 26.00 27.00 28.00 29.00 30^30
m 1 T J 1 \<X J • s* Itn
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GEOG. LONGITUOE (OEG. EAST)
Fig. 6: The effect of sunspot activity on the disruption probability in the
disturbed regions during the equinoxes.
D1 - 28
3.6 Changes in the critical level
Figures 3 and 7 illustrate the effect of changing the critical level or
fade margin (Xq) in the disruption probability calculations (equation (2)).
These figures represent the same situation except for the critical level. As
expected, increasing the critical level or fade margin decreases both the
area in which transionospheric propagation is likely to be disturbed by
scintillation effects and the probability of such disturbance. This is true
for both the equatorial and high latitude regions of high scintillation
activity.
3.7 Single circuit investigations
Besides obtaining instantaneous pictures of disruption probability over a
large geographic area at various times of day, season, etc., it is also
possible to employ the prediction scheme outlined in Section 2 to examine a
particular circuit in detail. Here the two terminals of the
transionospheric circuit are fixed at known positions so the disruption
probability can be examined as a function of time-of-day and day-of-year for
various operating frequencies, critical signal levels, SKp values and
sunspot numbers.
4. DISCUSSION
The prediction scheme used in the circuit performance evaluations
described above finds a mean scintillation index which is then converted to
a disruption probability (Section 2). No attempt is made to account for the
scatter individual scintillation index observations will have about the
predicted value. The whole process of irregularity and propagation
simulation is aimed at reducing this scatter. For instance, the present
scheme is a vast improvement, in this respect, over using a simple estimate
of mean index involving only a latitude variation. This is underscored by
the partial validation of the model as discussed in Section 2.5. Obviously
this scatter will be reduced further and the prediction scheme
correspondingly improved as more variables are taken into account in the
irregularity model. Even so, as the result of improvements which have
recently been made, the model is now quite realistic and allows meaningful
simulations of transionospheric propagation circuits to be made.
The examples of the use of the prediction scheme employed to illustrate
the discussion in the previous sections have all been based on a satellite
at synchronous height. It should be noted that the prediction scheme and,
indeed, the current computer programs embodying this scheme, are equally
applicable to orbiting satellites at any height.
D1 - 29
PROB LESS -4DB 1978 DAT 80
19.00 20.00 2.1.00
LOCAL TIME (HRS)
22-00 23.00 2M.00
_I L__ 1
1200Z 257MHZ RflSN 45 SKP 5
o
25.00 26.00 27.00 28.00 29.00 Jp3lO
S
'75.00
CONTOURS PRE 0/0
poo = HOHIZOH
MULTIPLT CONTOUR
NUMBERS BY
l.OE+OO
- K-K-X : S1 SBT
=>lu
Too ioiToo 120.00 lis. 00 150.00 issToo ieo.00 195.00 iToToo 225.00 "~ ilioToo 255.00 270.00
GEOG. LONGITUDE (DEG. ERST)
PROB LESS -8DB 1978 DRY 80 1200Z 257MHZ RflSN 45 SKP
CONTOURS PRE 0/0
: H0M20N
MULTIPLT CONTOUR
§ NUMBERS BT
l.OE+00
g— Z-2-Z = SI SBT
TOO 120.00 135.00 150.00 165.00 180.00 195.00 210.00 225.00 2li0.00 255.00 274.00
GEOG. LONGITUDE (DEG. ERST)
Fig. 7: The effect of changing the critical level in the disruption
probability calculations.
D1 - 30
REFERENCES
Basu,Sunanda, S.Basu and B.K.Khan (1976): Model of Equatorial
Scintillations from In-Situ Measurements. Radio Sci . , 11:821.
Booker, H.F. (1958): The Use of Radio Stars to Study Irregular Refraction of
Radio Waves in The Ionosphere. Proc. I .R.E. , 46:298.
Briggs,B.H. and I. A. Parkin (1963): On the Variation of Radio Star and
Satellite Scintillations with Zenith Angle. J. Atmosph.Terr .Phys . ,
25:339.
Fremouw,E.J. and H.F.Bates (1971): Worldwide Behaviour of Average VHF-UHF
Scintillations. Radio Sci. , 6:863.
Fremouw,E.J. and C.L.Rino (1973): An Empirical Model for Average F-Layer
Scintillation at VHF/UHF. Radio Sci. , 8:213.
Getmantsev,G.G. and L.M.Eroukhimov (1969): Radio Star and Satellite
Scintillations. Annals of the IQSY, 5:229.
Herman, J. R (1966): Spread F and Ionospheric F-region Irregularities. Rev,
of Geophys. , 4:255.
Nakagami,M. (1960): Statistical Methods in Radio-Wave Propagation. Edited
by W.C. Hoffman (Pergamon Press, New York) 3-36.
Singleton, D.G. (1970a): Saturation and Focusing Effects in Radio-Star and
Satellite Scintillations J . Atmosph . Terr . Phys . , 32:187.
Singleton, D.G. (1970b): The Effect of Irregularity Shape on Radio Star and
Satellite Scintillations J . Atmosph . Terr . Phys . , 32:315.
Singleton, D.G. (1975): An Empirical Model of Global Spread-F Occurrence.
J . Atmosph . Terr . Phys . , 37:1535.
Singleton, D.G. (1977): The Reconciliation of an F-Region Irregularity Model
with Sunspot-Cycle Variations in Spread-F Occurrence. Radio Sci . ,
12:107.
Singleton, D.G. (1978): An Improved Ionospheric Irregularity Model.
ERL-46-TR, Electronics Res. Lab., Dep. of Defence, Australia.
Whitney ,H.E. , J.Aarons, R.S.Allen and D.Seeman (1972): Estimation of the
Cumulative Amplitude Probability Distribution Function of Ionospheric
Scintillations. Radio Sci., 7:1095.
01 - 31
MODEL OF PHASE AND AMPLITUDE SCINTILLATIONS FROM IN-SITU MEASUREMENTS
Santimay Basu and Sunanda Basu
Emmanuel College, Boston, MA 02115
In-situ measurements of F-region Irregularity amplitude and ambient
electron density made by 0go-6 and AE-C satellites are utilized for
modelling phase and amplitude scintillations in the equatorial re-
gion during two solstice periods. Considerable differences in the
longitude variation is noted during the two solstices. The model
estimates are in good agreement with available ground-based phase
and amplitude scintillation measurements. Problems associated with
the use of bottomside spread-F data for transionospher ic propaga-
tion modelling at VHF/UHF are also discussed.
1. INTRODUCTION
F-region irregularities are the cause of intense scintillations (irregu-
lar phase and amplitude fluctuations} of signals transmitted through the
ionosphere over the frequency range VHF to 1 GHz at high latitudes and VHF to
S-band at equatorial latitudes. While the causative mechanisms of these ir-
regularities remain unresolved and continue to be a subject of multi-
technique experiments (Aarons et al . , 1978; Basu and Aarons, 1977; Basu and
Kelley, 1977; 1978), their effects are a cause of serious concern to communi-
cations engineers. This is because amplitude scintillations can degrade the
performance of high data rate satellite communication links while phase scin-
tillations can impair the performance of satellite systems that use synthetic
aperture processing to achieve high angular resolution.
Ground-based measurements over two decades have established the broad
morphological features of three major scintillation regions, two covering the
polar caps and a third one approximately centered on the magnetic equator
(Aarons, 1975). That spread-F observations broadly show similar occurrence
maxima have been documented in many studies (Shimazaki, 1959; Singleton, I960,
1968; Penndorf, 1962; Herman, 1966; Chandra and Rastogi, 1970). While un-
doubtedly both scintillations and spread-F are caused by irregularities in
the F-region, there are definite differences in the occurrence pattern of
each as a function of sunspot cycle, season and longitude. These will be dis-
cussed further in Section 2. Thus the use of bottomside spread-F data to
modify scintillation models at VHF/UHF must be treated with caution. Further-
more, both scintillation and spread-F measurements are performed primarily on
the ground and thus cannot provide coverage over ocean surfaces. Clustering
of geostationary satellites at preferred longitudes has also contributed to
Dl - 32
uneven scintillation coverage.
Satellites carrying out in-situ observations of irregularity parameters
present a viable alternative for mapping the irregularity morphology at both
high and low latitudes. At high latitudes this technique has been used by
Dyson (1969) and Sagalyn et al., (197M to map irregularity characteristics.
Good agreement was obtained between the scintillation boundary (Aarons and
Allen, 1971) and the in-situ irregularity boundary. However no attempt has
yet been made to convert the observed irregularity morphology into a high lat-
itude scintillation model. At the equator, Basu et al., (1976a, b) used in-
situ irregularity data obtained from Ogo-6 to map the equatorial irregularity
morphology and convert it into a scintillation model for the December sol-
stice. A pronounced longitude variation of equatorial scintillations was evi-
dent and comparison with available ground scintillation measurements was very
encouraging, indeed. In Section 3, the principle of utilizing the in-situ
technique for estimating phase and amplitude scintillations is presented. In
Section k we shall discuss earlier published results obtained with the Ogo-6
satellite and present more recent results obtained with the Atmosphere Ex-
plorer satellites. Available ground based scintillation data are used to
compare the model with actual observations. A brief summary is provided in
Section 5-
DIFFERENCES BETWEEN SPREAD-F AND SCINTILLATION MORPHOLOGY
The general association of spread-F and scintillations has been noted by
a large number of authors as mentioned before. The morphology of spread-F,
however, is better documented because of the large global network of iono-
sondes that was set up during the IGY period in 1957~58, many of which have
been kept operating subsequently. Scintillation morphology, in comparison,
is still inadequately explored and there are large gaps in our knowledge.
Thus in their first attempt at providing a global morphology of amplitude
scintillations, Fremouw and Rino (1973) found that more than 60% of their
thirty modelling categories had to remain untested because of a lack of data.
While it is probable that additional data may have been accumulated within
the last five years, we are still far from amassing a comprehensive scintil-
lation data bank. Thus, an effort has been made to utilize spread-F data to
modify scintillation models (Singleton, 1975; 1977; 1978). In this section,
we propose to discuss the geophysical parameters that control spread-F and
scintillation phenomena leading to differences in their occurrence pattern.
It is well known that scintillations are directly related to the rms
fluctuations of electron density, AN, and the thickness, L, of such irregu-
larity layers (Briggs and Parkin, 1963; Rufenach, 1975). Spread-F, on the
other hand, is generally characterized by Afrj, where frj is the critical fre-
quency of the F-layer. Since the electron density at the maximum of the
F-layer, N, is proportional to frj, the deviation of the electron density from
the mean, AN, should be proportional to frjAfo- Thus this latter quantity
should be used to compare with scintillation observations. Briggs (196M
could thus resolve the conflicting morphologies of spread-F data as observed
at Slough, and radio-star scintillation data observed at Cambridge over a
Dl - 33
solar cycle. As a result of this study Brlggs (1964) came to the conclusion
that the variation of the spread-F index with season and solar cycle reflects
mainly the variation of critical frequency with season and solar cycle. It is
interesting to note that Singleton (1962) using a different technique, namely
estimating frj and Afg from a number of stations at widely separated geomag-
netic latitudes, came to the same conclusion. He found that at all latitudes
the magnitude of Af is greatest when critical frequency is lowest. Thus, we
find that background conditions dominate the quantitative measure of the
spread-F index whereas the scintillation index is not similarly affected. A
quantitative relationship between in-situ irregularity measurements and
spread-F index was reported in a recent study by Wright et al . , (1977). They
showed that on a statistical basis, the magnitude of AN/N obtained by Ogo-6
can be related to 2Af/f read from frequency spread ionograms. This is in
agreement with the arguments given above.
Another major problem of using spread-F as an ionospheric irregularity
index is the great variation of equipment and convention used to measure and
classify spread-F. This point was discussed at some length by Lyon et al.,
(i960), where they pointed out that the 50 percent reduction of spread-F
occurrence during the equinoxes in the American zone as compared to the Afro-
Indian zone shown in their Figure 1 is due to equipment differences. The
fast-sweep high-power ionosondes being used at Huancayo and Chimbote in the
American sector were reponsible for obtaining better quality ionograms from
which frjF could be read even in the presence of spreading and hence a smaller
number of occurrences of spread-F were reported. A careful analysis of the
Huancayo and Ibadan (in the African sector) ionograms by the authors them-
selves showed no significant variation. However, the results of Lyon et al.,
(i960) have been used by Singleton (1978) to modify the Fremouw-Rino scintil-
lation model leading to a prediction of much lower equinoctial occurrence of
scintillations in the American sector as compared to a station in the African
sector. This is contrary to scintillation observations as may be noted by
comparing Figures 3 and 6 of Aarons (1977)- It is thus quite probable that
large errors will be introduced into existing scintillation models by modi-
fying them in such a way as to reproduce faithfully tabulated bottomside
spread-F occurrence characteristics.
The problems associated with the modelling of scintillations based on
spread-F data can be further recognized by a discussion of several known in-
stances of ant i -correlat ion in their occurrence characteristics. At high
latitudes studies conducted by Penndorf (1962), Tao (1965) and Olesen and
Jepsen (1966) have all conclusively proved that spread-F in all sectors of the
northern hemisphere auroral oval show a winter maximum and summer minimum.
Scintillations in the North Atlantic sector of the auroral oval, on the other
hand, show a consistent summer maximum and winter minimum as shown in Figure
1 for data from Narssarssuaq , Greenland. This diagram reproduced from Basu
(1975) was obtained by updating the data analysis made by the Air Force Geo-
physics Laboratory group (Aarons, 1973a, b; Whitney et al., 1973) and convert-
ing to S/j using Whitney's (197*0 method. Analysis of more recent data upto
1976 shows an exactly similar seasonal variation (J. Aarons, private commun-
ication, 1977).
Basu (1975) showed that the two-to-one variation of the SZ+ index is in
keeping with the same magnitude of variation of the auroral electrojet index
AL (Davis and Sugiura, 1966) in the North Atlantic sector which itself may be
caused by the variation of the orientation angle x of the earth's magnetic
Dl - 3^
100
a?
o
ro
A
<r
</)
UJ
»-
UJ
<
Z
UJ
o
QC
UJ
Q.
Fig. 1
80
60
40
20
PERCENT
OCCURRENCE
MEAN S4
1968
_J L
1969
__l L
1970
_l L
1971
i
1972
L__
0.6
0.4 *
<
UJ
0.2
FWSSuFW SSuFWSSuFWSSuF
The seasonal behaviour of percentage occurrence of S/j > 0.3 (SI > 6dB)
shown by circles and mean S/j index (triangles) recorded at Narssar-
ssuaq, Greenland from ATS-3 at 137 MHz between Sept 1968 and Oct 1972
for Kp = 0~3- The mean of the two highest hourly values of percen-
tage occurrence and S/+ index in the 2200-0200 LT period in each
season has been plotted (after Basu, 1975).
dipole with respect to the solar wind flow. It was further pointed out that
such a pronounced seasonal variation may not be" expected in the Scandinavian
and Alaskan sectors of the auroral oval where the seasonal variation of the
dipole tilt angle x is much smaller. In agreement with the above prediction,
earlier radio star measurements in the Alaskan sector (E.J. Fremouw, private
communication, 1975) and satellite scintillation measurements in the Scandin-
avian sector (Liszka, 1963) and more recent WIDEBAND satellite observations
in Alaska (C.L. Rino, private communication, 1978) failed to show any notice-
able seasonal variation. Thus there is a longitudinal control of the seasonal
pattern of scintillation occurrence in the auroral oval which is not possible
to model on the basis of spread-F observations.
Other examples of major discrepancy between scintillation and spread-F
data may be found in the equatorial region. The seasonal spread-F occurrence
maximizes at African longitudes during the June solstice (Lyon et al., I960).
This is in contrast to the minimum of scintillation occurrence observed at
Legon , Ghana as shown in Figure 2 which is reproduced from Koster (1978).
This data has been obtained at high elevation angles using Marisat trans-
Dl
35
missions at 257 MHz and unambiguously shows the minimum occurrence of scintil-
lations during the June solstice. Differences in sunspot cycle variation are
also observed. For example, spread-F shows a negative correlation with sun-
spot cycle at Huancayo (Chandra and Rastogi, 1970) while scintillations show a
positive correlation (Aarons, 1977)- Chandra and Rastogi's work did not dis-
tinguish data on the basis of magnetic activity but a more recent analysis
has shown that the negative correlation holds even for magnetically quiet days
(J. Aarons, private communication, 1979). Further, to simultaneously model
scintillation and spread-F characteristics observed at Legon by Koster and
Wright (i960), Singleton (1978) found that a variation of L, the thickness of
the irregularity layer, from 10 km at 1800 LT to 100 km at 2^00 LT and finally
to 1000 km at 0600 LT is necessary. There is no physical basis for postu-
lating such an irregularity layer thickness variation, indeed, it is contrary
to Jicamarca radar measurements which show that irregularity layer thickness
is maximum in the evening hours when scintillations also maximize (Basu et
al., 1977; 1978). Such ad-hoc parameter variations to match observed spread-
F and scintillation characteristics in one region is liable to cause large
errors in scintillation modelling at another location.
MARISAT 257 MHz GHANA
18 20 22 00 2 4
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
JAN
FEB
MAR
"I 1 1 r
20 22 00 2
LOCAL TIME (HRS)
Fig. 2 Percentage occurrence contours of scintillation index Sl| ^ 0.3
(SI > 6 dB) at 257 MHz obtained at Ghana from Marisat observations
(after Koster, 1978).
Dl - 36
3. THE TECHNIQUE OF MODELLING SCINTILLATIONS FROM IN-SITU DATA
A measure of the temporal fluctuations or scintillations of signal phase
and amplitude which is recorded by a receiver on the ground is provided by
the scintillation index (Briggs and Parkin, 1963). The normalized second
central moment of signal intensity (l) is used to represent the S/^ index of
amplitude fluctuations given by
2 T2" - m2
S,, = ' *U (1)
'k
(T)
On the other hand, the index of temporal phase fluctuations is represented by
the variance in phase, a?.
In the framework of diffraction theory, the indices of phase (a*) and
amplitude (S^) fluctuations can be related to the irregularity parameters in
the ionosphere. Initially, the above relationship was developed for an
assumed gaussian form of irregularities. However, Dyson et al., (197*0 and
Phelps and Sagalyn (1976) showed by the use of in-situ data that the irregu-
larities at F-region heights do have a power law type of irregularity power
spectrum with one-dimensional spectral index of 2 corresponding to a 3~dimen-
sional index of h. For such a 3~d imensional irregularity power spectrum with
an outer scale wavenumber Kq, the variance of phase (a|) and amplitude scin-
tillation index ( S/4 ) in the case of weak scattering have been obtained (Rino
and Matthews, 1978) as
a? =
(reX)2 • (Lsec6) <AN2> KQG (iveff)2 (2)
2TT2
S2 = ^2 . (reA)2 • (LsecO) <AN2> ^g^ KQF (3)
where
- the classical electron radius (2.8 x 10"'-5 m)
- the wavelength of probing radio wave
- irregularity layer height and thickness respectively
- zenith angle at irregularity height
- mean square electron density deviation
- outer scale wavenumber
- detrend interval and effective scan velocity of the propaga-
tion path across the irregularities
G,F - geometrical parameters for anisotropic irregularities.
Equation (3) shows that the S^ index of scintillation can be modelled if
information on electron density deviation, AN, and the outer scale wavenumber,
Kq and irregularity layer thickness are available. The axial ratios perti-
nent to the three dimensional shape of the irregularities (rod or sheet)
enter into the geometrical factors G and F in equations (2) and (3)
Dl - 37
re
X
Z,L
e
<AN2>
K0
T»veff
respectively. The available in-situ data do not provide information on G and
F and the shape of the irregularities have to be assumed. The modelling of
phase variance in equation (2) is related to two additional parameters veff
and i as discussed by Rino and Matthews (1978). The parameter, veff, depends
not only on the relative velocity between the propagation path and the irreg-
ularities but for anisotropic irregularities, on the direction of motion with
respect to the shortest autocorrelation distance of electron density devia-
tion as well. The detrend interval x is set by the time interval over which
the phase variance is to be computed. Thus veff and i are set by the parti-
cular system for which the phase modelling is to be done.
The major geophysical parameters involved in the modelling of S/4 and Oa
are thus the rms electron density deviation, AN, the form of irregularity
power spectrum, the outer-scale wavenumber, Kq , and the irregularity layer
thickness, L. Various types of analyzers on board the satellites have been
used to measure the ion concentration (or electron concentration for charge
neutrality) at F-region heights (Hanson et al., 1970; Sagalyn et al., 197^).
Currently, it is possible to sample the ion or electron concentration (N)
with an accuracy of .01% at a sampling rate as high as 200 per sec corres-
ponding to a spatial resolution of 35 m (McClure and Hanson, 1973; McClure
et al., 1977). Such high resolution data have been used to obtain the ir-
regularity power spectrum which, as already mentioned, indicate that at F
region heights power-law type of irregularity power spectrum is obtained with
a 3~d imens ional spectral index of h. This type of spectrum forms the basis
of model equations (2) and (3) given above.
For the development of a morphological model of scintillations, measure-
ments of irregularity amplitude, AN/N, as computed from T sec of data are
utilized in conjunction with simultaneous measurement of electron density N.
A combination of AN/N and N data provides the required AN parameter as a
function of position and time. In case the satellite altitude is much lower
than the height of maximum ionization, proper allowance should be made in
deriving AN estimates. The in-situ measurements of irregularity spectrum
(Dyson et al., 197^; Phelps and Sagalyn, 1976; McClure, private communication,
1978) and phase scintillation measurements (Rino and Matthews, 1978) with
Wideband satellite indicate that the outer scale at F region heights is large,
probably on the order of tens of km. In view of this, the spatial length
corresponding to T sec time interval when projected in the direction of
shortest correlation distance of electron density deviation sets the apparent
outer scale length qQ. The outer scale wavenumber is, therefore, Ko=2iT/qQ.
For the equatorial scintillation model that we developed from the 0go-6 in-
situ observations, the time interval was T=5 sees and the outer scale length
was considered to be 20 km corresponding to an outer-scale wavenumber of
K0 - 0.3 km"l.
The satellite in-situ measurements pertain to a single altitude and can-
not directly provide any information on irregularity layer thickness (l_).
However, it is possible to obtain estimates of this parameter from in-situ
data obtained by satellites in elliptic orbit or direct radar backscatter
observations (Basu et al., 1976; Woodman and LaHoz, 1976). Based on these
measurements, it is found that L = 200 km is appropriate for equatorial scin-
tillation modelling. It should be emphasized that the electron density de-
vation (AN) of the irregularities is the single parameter which is most
variable and controls scintillations. The importance of the in-situ tech-
nique stems from the fact that it directly samples the fluctuations of
Dl - 38
electron density,
k. SCINTILLATION MODEL DEVELOPED FROM IN-SITU DATA
k.] Equatorial Model during the December Solstice
Based on the Ogo-6 in-situ irregularity data obtained during November-
December, 1969 and 1970 when the satellite perigee (^00 km altitude) was
located over the equatorial region, an occurrence contour of AN = 10^ m~3
was derived during the early evening hours (1900-2300 MLT) between ±2k° dip
latitudes at all longitudes (Basu et al., 1976a, b). Considering an outer
scale wavenumber Kq = 0.31 km-', equatorial irregularity layer thickness of
200 km and median altitude of *+50 km, the above level of AN was translated
to an amplitude scintillation index of S/j = 0.2^ (or a peak-to-peak fluctu-
ation of k.S dB) at ]h0 MHz for overhead propagation geometry. The percen-
tage occurrence contour of the above level of equatorial scintillation during
the D months (November-December) in the early evening hours under sunspot
maximum conditions is shown in Figure 3. The pronounced longitude variation
of scintillation predicted by this model and its agreement with ground scin-
tillation measurements have been discussed at length in Basu et al.,
(1976a, b).
Since we consider that the data length providing AN dictates the value
of Kq, we may put veff t = 2tt/Kq = 20 x 10^ m in equation (2) and derive that
for AN = 10^0 m~3 under overhead propagation condition o§ = 2.2 radians at
1 *t0 MHz. For nighttime geostationary satellite observations in the equator-
ial region, veff = 100 m/sec corresponding to the irregularity drift and
therefore, Figure 3 may represent the occurrence contours of 0$ Z 2.2 radians
at 1^0 MHz with a detrend interval of t = 200 sees. Since a^ scales linearly
with t and the radio wavelength, the above statistics are equivalent to a^ ^
0.01 radian at 1^00 MHz with t = 10 sees. These estimates will also apply to
an orbiting satellite if the flight path is aligned parallel to the geomag-
netic field when veff becomes equal to the E-W drift of the irregularities.
This is nearly achieved by the Wideband satellite in the Peruvian sector. A
limited set of phase scintillation data obtained from the Wideband satellite
at Ancon , Peru (kindly made available to us by C.L. Rino of SRI International)
during 1977 indicate that the average value of cu - .05 radian at 1239 MHz
with x = 10 sees at the magnetic equator for near overhead propagation con-
ditions. This is in fair agreement with our estimates.
h .2 Equatorial Model during the June Solstice
The 0go-6 satellite, during its two=year lifetime, did not achieve a
suitable per igee-cum-local time combination for equatorial irregularity
modelling during the June solstice. Recently, it has been possible to
utilize the Atmospheric Explorer-C (to be abbreviated as AE-C) in-situ
Dl - 39
SCINTILLATION ESTIMATE FROM 0G0-6 DATA
+ 160
160
-120
-80
-40 0 +40
GEOGRAPHIC LONGITUDE
+ 160
Fig. 3 Percentage occurrence contours of amplitude scintillation index
S^ - 0.24 (SI > k.5 dB) or phase scintillation index a<j> > 0.1 radian
with a detrend interval of t = 10 sees at 140 MHz (1900-2300 MLT,
Nov-Dec, 1969 and 1970) obtained from 0go-6 in-situ irregularity
data for overhead geometry.
irregularity data for deve
the J months (June-July).
600 km over the equatorial
study of F region irregula
coverage of AE-C satellite
tained on a specific night
number of transits availab
a similar technique as out
occurrence contours of ele
within ±2k° dip latitude a
2330 MLT under magncticall
Figure k. As discussed be
to an amplitude scintillat
ation of 4.5 dB) at 140 MH
equivalent to phase scinti
detrend interval of t = 10
10 sees for geostationary
loping an equatorial scintillation model during
The satellite altitude varied from about 200 -
region and provided an ideal platform for the
rities. Unfortunately, however, the longitude
was not uniform and only a few orbits were ob-
This resulted in a great reduction of the total
le within a specific local time period. Employing
lined in the previous subsection, the percentage
ctron density deviation AN ^ 10^0 m~3 was obtained
t all longitudes in the J months during 1900-
y quiet conditions (Kp = 0-3) and is shown in
fore, the above level of AN = 10'^ m~3 corresponds
ion index of Sh, = 0.24 (or a peak-to-peak fluctu-
z for overhead propagation conditions which is
llations of o^ = 0.1 radian at 140 MHz with a
sees or o§ = 0.01 radian at 1400 MHz with t =
satellite observations near the magnetic equator.
01 - 40
Figure h indicates that there is a drastic reduction of scint i 1 lal t ion
occurrence in the pre-midn ight period during the J months as compared to the
occurrence characteristics shown in Figure 3 for the same time interval
during the D months, particularly in the African and American sectors. It
should, however, be noted that Figures 3 and k represent respectively the
sunspot maximum and minimum conditions. The reduction of scintillation
occurrence in the pre-midnight period at African and American longitudes
during the J months as predicted by Figure k is in good agreement with the
ground scintillation observations at Huancayo (HU) and Legon (LE) during the
same period as will be discussed later. Figure 5 shows the occurrence
statistics of an identical level of scintillation obtained from AE-C in-situ
data during the J months but in the near and post-midnight period. The
observing period encompassed two magnetic storms but due to paucity of data
separation on the basis of magnetic activity levels was not possible. The
longitude sectors shown shaded indicate that due to reduced number of
SCINTILLATION ESTIMATE FROM AE-C DATA
-80 -40 0 40
GEOGRAPHIC LONGITUDE
160
Fig. k Percentage occurrence contours of amplitude scintillation index
SZj - 0.24 (SI ^ h.5 dB) or phase scintillation index a^ > 0.1 radian
with a detrend interval of t = 10 sees at \k0 MHz (1900-2330 MLT,
July 1 1 -Aug h, 197^, magnetically quiet conditions) obtained from
in-situ irregularity measurements by Atmospheric Explorer-C (AE-C)
satellite for overhead geometry.
Dl - k]
SCINTILLATION ESTIMATE FROM AE-C DATA
UJ
Q
<
_l
Q.
Q
-20
160 -160
-120 -80
-40 0 40 80
GEOGRAPHIC LONGITUDE
140 160
Fig. 5 Percentage occurrence contours of amplitude scintillations with
S/j > 0.24 (SI > k.5 dB) or phase scintillations with o$ > 0.1 radian
with a detrend interval of t = 10 sees at ]k0 MHz (2330-0300 MLT,
June 20-July 9, 197^, magnetically quiet and disturbed conditions)
obtained from AE-C in-situ data for overhead geometry.
transits the statistics over these regions is unreliable. Considering the
remaining portions of the diagram, a general enhancement of scintillation
occurrence may be noted at all longitudes.
In order to compare the occurrence statistics of scintillations during
the J-months developed from in-situ data (Figures h and 5) with ground ob-
servations we present in Figures 6 and 7 the nighttime patterns of scintil-
lation occurrence for the low (Kp = 0-3) and high (Kp = k~3) magnetic in-
dices observed during the same period at Huancayo, Peru and Legon , Ghana,
respectively. Figure 6 shows the statistics of SI > 4 dB obtained at
Huancayo during June-July, 197^ from 137 MHz transmissions of ATS-3 whereas
Figure 7 shows the statistics of SI > 6 dB observed at Legon from the same
satellite. A higher level of scintillation index was chosen for Legon to
account for the lower elevation angle of ATS-3 satellite when viewed from
this station. Figure 6 indicates that at Huancayo, the occurrence of scin-
tillations is as low as 10% in the pre-midnight period during the J months
under magnetically quiet conditions. This is in good agreement with the 15%
occurrence near Huancayo derived from in-situ data under quiet periods
Dl - hi
137 MHz A- 3 HUANCAYO
JUN/JUL 1974
GD
T>
A
»—i
(/)
Ul
o
UJ
or
or
O
o
o
o
or
UJ
50-i
40-
30-
20-
10-
21
T 1 r
23 01 03
LOCAL TIME
05
07
Fig. 6 Variation of the percentage occurrence of scintillations SI > k dB
at 137 MHz observed at Huancayo with ATS-3 satellite at 70° elevation
during June-July, 197^, for magnetically quiet (Kp ^ 0-3) and dis-
turbed (Kp ^ h~3) conditions (data courtesy of Instituto Geophysico
del Peru).
(Kp = 0-3) and shown in Figure k. Figure 6 shows
active conditions, the occurrence of scintillation
increase of scintillation with magnetic activity i
during the J months has been documented before (Mu
As mentioned earlier, the statistics of scintillat
data during the midnight and post-midnight period
tions (Kp = 0-9) and shown in Figure 5 encompassed
fact, all the AE-C transits in this figure that re
between -20° and -100° longitudes occurred during
enhanced scintillation in the Huancayo sector pred
corresponds very well with the observational resul
that under magnetically
is greatly enhanced. The
n the Huancayo sector
Hen, 1973; Aarons, 1977).
ions obtained from in-situ
for all magnetic condi-
two magnetic storms. In
corded irregularities
disturbed period. The
icted by Figure 5 thus
ts shown in Figure 6.
01 - 43
UJ
o
z
UJ
or
or
o
o
o
UJ
u
or
UJ
0_
37MHz A-3 GHANA
JUN/JUL 1974
_ 50i
m
(0
t 40-
30-
20-
10-
L0CAL TIME
Fig. 7 Variation of the percentage occurrence of scintillations SI > 6 dB
at 137 MHz observed at Legon with ATS-3 satellite at 12° elevation
during June-July, 197^, for magnetically quiet (Kp ^ 0-3) and dis-
turbed (Kp ^ h~3) conditions. In view of the low elevation angle of
the satellite, the occurrence diagram for SI > 6 dB in this diagram
is compatible with SI > k dB in Figure 6 (data courtesy of J.R.
Koster) .
Figure 7 shows the behavior of ground scintillation results at Legon
(J.R. Koster, private communication, 1978) during June-July, 197^ and indi-
cates that under magnetically quiet conditions (Kp = 0-3), a scintillation
occurrence of about 20% is obtained primarily in the pre-midnight period.
Contrary to the usual inverse correlation with magnetic activity (Aarons,
1977), Figure 7 shows enhanced scintillation occurrence during magnetic
activity. The enhancement observed in the present data set is confined to
the pre-midnight hours. This behavior is somewhat different from that noted
in the Huancayo sector (Figure 6) where enhancement of scintillation
occurred during both pre- and post-midnight periods. The quiettime occur-
rence of scintillation observed at Legon and shown in Figure 7 is in agree-
ment with the quiettime statistics obtained with the in-situ data around
Legon (LE) as shown in Figure k. The behavior of scintillations in this
sector obtained from in-situ data during the post-midnight period (Figure 5)
Dl - kk
could not, however, be compared with the observational results as the number
of AE-C transits over the Legon sector was very small.
Combining Figures 3, k , and 5, it may be noted that the occurrence of
scintillations at Kwajalein (KW) is highest in the J-months during the post-
midnight period. This is in agreement with the observations of SRI Inter-
national performed at Kwajalein during 1977 (Rino et al., 1 977) -
It should, however, be noted that while Figure 3 providing the statistics
of scintillation during the D-months was based on 250 transits of 0go-6
satellite, Figures k and 5 providing the occurrence statistics during the J-
months were based on a total of only 105 transits of AE-C satellite. The
estimates should therefore be considered preliminary and we are currently
attempting to enlarge the data base by using other available satellites.
CONCLUSIONS
The satellite in-situ irregularity measurements provide a direct measure-
ment of electron density deviation (AN) parameter which can be used to de-
velop models for amplitude and phase scintillations. In view of the insuf-
ficient coverage of ground scintillation observations caused by either the
absence of suitable ground locations or satellites, the usefulness of in-
situ probing with unlimited latitude and longitude coverage cannot be over-
emphasized. The evaluations made in the previous section show that scin-
tillation models based on the quantitative measure of electron density de-
viation (AN) by satellites provide realistic estimates. Although, the
models that we have developed so far pertain to the equatorial region, it is
by no means limited to this region. Currently, a high latitude scintilla-
tion model based on AE-C and AE-D data is being developed.
It should, however, be mentioned that our current efforts are based on
satellites whose primary function was not concerned with irregularity
measurements at F region heights for scintillation modelling. As such, the
constraints imposed on satellite altitude, time of transit, etc., limited
our data base. A dedicated satellite performing such measurements at F-
region altitudes with suitable orbital characteristics will be an ideal
vehicle for the development of a world-wide model of phase and amplitude
scint i 1 lat ions .
6. ACKNOWLEDGMENTS
The 0go-6 and AE-C satellite data were kindly made available to us by
W.B. Hanson and J. P. McClure. Phase and amplitude scintillation data were
kindly provided by C.L. Rino, J.R. Koster and A. Bushby. A helpful critique
of the manuscript by J. Aarons is gratefully acknowledged. We wish to thank
J. Freni for help with AE-C data analysis.
This work was partially supported by AFGL contract Fl 9628-78-C-OOO5 and
NASA contract S-*4l8^3B.
Dl - kS
7. REFERENCES
Aarons, J. (1973a): A descriptive model of F-layer high-latitude irregular-
ities as shown by scintillation observations. J . Geophys . Res . , 78:
7441.
Aarons, J. (1973b): A graphical description of scintillation occurrence
patterns, in Agardograph No. 166 on Total Electron Content and Scintil-
lation Studies of the Ionosphere, edited by J. Aarons, North Atlantic
Treaty Organization, Neuilly Sur Seine, France.
Aarons, J. (1975): Global morphology of ionospheric scintillations II,
AFCRL Report No. TR-75-01 35 , Air Force Cambridge Research Laboratories,
Hanscom AFB, MA 01731 .
Aarons, J. (1977): Equatorial scintillations: A review. IEEE Trans. Ant.
& Propagat. , 25:729- ~~
Aarons, J., and R.S. Allen (1971): Scintillation boundary during quiet and
disturbed magnetic conditions. J . Geophys . Res. , 76:170.
Aarons, J., J. Buchau, S. Basu, and J. P. McClure (1978): The localized
origin of equatorial F-region irregularity patches. J . Geophys . Res . ,
83:1659.
Basu, S. (1975): Universal time seasonal variations of auroral zone magne-
tic activity and VHF scintillations. J. Geophys. Res. , 80:4725.
Basu, S., and J. Aarons (1977): E-quatorial irregularity campaigns, Part I:
Correlated scintillation and radar backscatter measurements in October,
1976. AFGL Report No. TR-77-0264, Air Force Geophysics Laboratory,
Hanscom AFB, MA 01731 .
Basu, S., and M.C. Kelley (1977): Review of equatorial scintillation phen-
omena in light of recent developments in the theory and measurement of
equatorial irregularities. J. Atmos. Terr. Phys., 39:1229.
Basu, S. , and M.C. Kelley (1978): A review of recent observations of equa-
torial scintillations and their relationship to current theories of F-
region irregularity generation. Accepted by Rad ?o Sc ? .
Basu, S., S. Basu, J.N. Bhar, and B.K. Guhathakurta (1976a): Equatorial
irregularity morphology in the Afro-Asian sector with 0go-6. Space
Res. , 16:427.
Basu, S., S. Basu, and B.K. Khan (1976b): Model of equatorial scintilla-
tions from in-situ measurements. Radio Sc i . , 11:821.
Dl - 46
Basu, S., J. Aarons, J. P. McClure, C. LaHoz, A. Bushby, and R.F. Woodman
(1977): Preliminary comparisons of VHF radar maps of F-region irregu-
larities with scintillations in the equatorial region. J. Atmos. Terr.
Phys. , 39:1251 .
Basu, S., S. Basu, J. Aarons, J. P. McClure, and M.D. Cousins (1978): On the
coexistence of km- and m-scale irregularities in the nighttime equator-
ial F-region. J . Geophys . Res . , 83:4219
Briggs, B.H. (1964): Observations of radio star scintillations and spread-
F echoes over a solar cycle. J. Atmos. Terr. Phys., 26:1.
Briggs, B.H., and I .A. Parkin (1963): On the variation of radio star and
satellite scintillation with zenith angle. J. Atmos. Terr. Phys., 25:
339.
Chandra, H., and R.G. Rastogi (1970): Solar cycle and seasonal variation of
spread-F near the magnetic equator. J. Atmos. Terr. Phys., 32:439-
Davis, T.N., and M. Sugiura (1966): Auroral electrojet activity index AE
and its universal time variations. J . Geophys. Res . , 71:785-
Dyson, P.L. (1969): Direct measurements of the size and amplitude of ir-
regularities in the topside ionosphere. J. Geophys . Res . , 74:6291-
Dyson, P.L., J. P. McClure, and W.B. Hanson (197*0: In-situ measurements of
the spectral characteristics of F-region ionospheric irregularities.
J. Geophys. Res., 79:1495-
Fremouw, E.J., and C.L. Rino (1973): An empirical model of average F-layer
scintillation at VHF/UHF. Radio Sci . , 8:213-
Hanson, W.B., S. Sanatani, D. Zuccaro, and T.W. Flowerday (1970): Plasma
measurements with the retarding potential analyzer on 0go-6. J .
Geophys. Res., 75 : 5^83 -
Herman, J.R. (1966): Spread-F and ionospheric T-reg ion irregularities.
Rev. Geophys. Space Phys., 4:255-
Kelleher, R.F. (1976): Morphology of equatorial spread-F irregularities in
Proceedings of Fifth International Equatorial Aeronomy Symposium,
Townsville, Australia.
Koster, J.R. (1978): Phase and amplitude scintillation at the equator,
Final Scientific Report on Grant No. AFOSR-78-351 6, University of Ghana,
Legon , Ghana,
Koster, J.R., and R.W.H. Wright (I960): Scintillation, spread-F and trans-
equatorial scatter. J . Geophys . Res . , 65:2303-
Liszka, L. (1963): A study of ionospheric irregularities using trans-
missions at 54 Mc/s. Ark. Geofys. , 4:227-
Dl - 47
Lyon, A.J., N.J. Skinner, and R.W.H. Wright (i960): The belt of equatorial
spread-F. J. Atmos. Terr. Phys., 19:1^5.
McClure, J. P., and W.B. Hanson (1973): A catalog of ionospheric F-region
irregularity behavior based on Ogo-6 retarding potential analyzer data.
J. Geophys. Res., 78 : 7^31 •
McClure, J. P., W.B. Hanson, and J.H. Hoffman (1977): Plasma bubbles and
irregularities in the equatorial ionosphere. J . Geophys . Res . , 82:
2650.
Mullen, J. P. (1973): Sensitivity of equatorial scintillation to magnetic
activity, J. Atmos. Terr. Phys. , 35:1187.
Olesen, J.K., and S.B. Jepsen (1966): Some characteristics of spread-F in
very high latitudes, in Spread-F and Its Effects upon Radiowave Propa-
gation and Communications, edited by P. Newman, Techn i vi s ion , Maiden-
head, England.
Penndorf, R. (1962): Diurnal and seasonal variation of spread-F in the
Arctic. J. Geophys. Res. , 67:2289.
Phelps, A.D.R., and R.C. Sagalyn (1976): Plasma density irregularities in
the high latitude top side ionosphere. J . Geophys . Res . , 81:515.
Rino, C.L., and S.J. Matthews (1978): On the interpretation of ionospheric
scintillation data using a power law phase screen model - weak scatter.
SRI Report No. 4606T, SRI International Menlo Park, CA 9^025.
Rino, C.L., E.J. Fremouw, R.C. Livingston, M.D. Cousins, and B.C. Fair
(1977): Wideband satellite observations, SRI Report No. DNA *+399F,
SRI International, Menlo Park, CA 9^025.
Rufenach, C.L. (1975): Ionospheric scintillation by a random phase screen:
Spectral approach. Radio Sci . , 10:155.
Singleton, D.G. (i960): The geomorphology of spread F. J . Geophys . Res . ,
65:3615.
Singleton, D.G. (1962): Spread-F and the perturbations of the maximum elec-
tron density of the F-layer. Aust . J . Phys. , 15:262.
Singleton, D.G. (1968): The morphology of spread-F occurrence over half a
sunspot cycle. J . Geophys . Res . , 73:295-
Singleton, D.G. (1975): An empirical model of global spread-F occurrence.
J. Atmos. Terr. Phys. , 37:1535.
Singleton, D.G. (1977): The reconciliation of an F-region irregularity
model with sunspot cycle variations in spread-F occurrence. Radio Sci . ,
12:107.
Dl - i»8
Singleton, D.G. (1978): Improving the ionospheric irregularity model.
Sumbitted to J. Geophys. Res.
Tao, K. (1965): Worldwide maps of the occurrence percentage of spread-F in
years of high and low sunspot numbers. J. Radio Res . Lab. , 12:317.
Whitney, H.E., J. Aarons, R.S. Allen, and D.R. Seeman (1973): Cumulative
amplitude probability distribution functions for three observatories,
in Agardograph No. 166 on Total Electron Content and Scintillation
Studies of the Ionosphere, edited by J. Aarons, North Atlantic Treaty
Organization, Neuilly Sur Seine, France.
Whitney, H.E. (197*0: Notes on the relationship of scintillation index to
probability distributions and their uses for system design, Report No.
AFCRL-TR-7*»-OOOi4, Air Force Cambridge Research Laboratories, Bedford,
MA.
Woodman, R.F., and C. LaHoz (1976): Radar observations of F-region equa-
torial irregularities. J. Geophys. Res. , 81:5^7-
Wright, J.W., J. P. McClure, and W.B. Hanson (1977): Comparisons of iono-
gram and Ogo-6 satellite observations of small-scale F-region inhomo-
geneities. J. Geophys. Res. , 82 : 5*+8 .
D1 - A9
A RESUME OF ANTICIPATED FLEETSATCOM AND GAPFILLER
SCINTILLATION EFFECTS DURING THE PEAK OF SOLAR
CYCLE 21 (1980-1982)
John M. Goodman
Head, Telecommuni cat ions Environmental Effects Branch
Communications Sciences Division
Naval Research Laboratory
4555 Overlook Ave., S.W.
Washington, D. C. 20375, USA
A brief review of UHF scintillation data obtained worldwide,
and particularly over the magnetic equator, combined with
projections for a significant peak in solar activity occurring
in 1981 implies that significant degradation in communication
performance will occur under certain conditions. This paper
describes some of the characteristics of amplitude and phase
scintillation as we know them, examines the trends with solar
and magnetic activity, and projects the trends into the near
future.
1.0 Prospectus
The amplitude scintillation of radiostar emissions and
transmissions from artificial earth satellites has been of considerable
interest to radio engineers for several decades. Generally speaking it
has been found that amplitude scintillation increases with both
increasing solar activity and magnetic activity, but it has marked
variations with latitude and time of day. There have been found to
exist two intense zones of scintillations; one at high latitudes, and
the other centered over the geomagnetic equator. Apart from these
latitudinal-referenced zones, a longitudinal variation in the
occurrence of amplitude scintillation has also been detected for fixed
universal times. Weak scintillation has been observed at mid-latitudes
but this is predominantly a summer-daytime phenomenon which is likely
the result of sporadic E-ionization. It is thought that high latitude
scintillation results from particle precipitation events concommitant
with substorms and that equatorial scintillation derives from an
instability (Rayleigh-Taylor) in that region, which is most pronounced
D1 - 50
during nocturnal and equinoctial periods. Scintillation has been
observed to decrease with increasing radio frequency (f-^*^) and
increasing elevation angle. Strong UHF scintillation has been observed
at high latitudes and scintillation at GHz frequencies has been
observed over the geomagnetic equator. There is an equatorward
expansion of the high-latitude scintillation zone and a poleward
expansion of the equatorial zone suggested by recent NTS-2 data at both
UHF and L-band following geomagnetic storms. Since geomagnetic storms
ultimately derive from solar activity, the globally-averaged
scintillation is typically expected to increase as we approach the high
in solar activity. As a result disrupted UHF communication may occur
at certain midlatitude stations and almost certainly will involve
communication stations and ships at high latitudes.
The amplitude distributions associated with scintillation events
are typically observed to be approximated by a Nakagami-m function
which allows for Rayleigh fading with m=l . It has been observed that
Rayleigh (essentially worst-cast) fading is the rule, rather than the
exception during peak scintillation periods at UHF.
The power spectra are dominated by contributions near the
Fresnel-zone frequency v.(XZ)-2 when v is the relative velocity of
ionospheric motion, X is the radio wavelength and Z is the distance to
the scintillation region of inhomogeneities , which have been found to
exhibit a power law spectral behavior. As deduced from various
experimental techniques, the height distribution of inhomogeneities
favors a mean height of ~ 400 kilometers for its centroid, but this
varies widely depending both upon geography and forcing function
dependencies. Thus at a FLEETSATCOM or MARISAT/GAPFILLER frequency
of ~ 250 MHz and a relative velocity of 200 meters/sec, we anticipate
that most of the scintillation power will occur at roughly 0.3 Hz which
implies an average fading interval of the order of 3 seconds but may
become significantly shorter as the intensity of the scatter becomes
larger in the Rayleigh regime (due to multiple scattering). This
periodicity is clearly expected to vary with solar activity (i.e.,
fades to become faster as well as deeper with increasing activity)
because of enhanced motion of the inhomogeneities (i.e., dependence on
v, above). The scintillation power spectra typically have a power-law
behavior, V ^, above the Fresnel frequency where V is the fluctuation
frequency and the index p ranges between about 2 and 4 ( p is taken to
around 3 on the average but may be slightly lower at high latitudes and
higher at low latitudes, depending on geomagnetic activity.) This
behavior is brought about by the fact that the intrinsic spectra of
inhomogeneities is of a power-law form rather than being Gaussian, as
originally supposed, and it accounts at least in part for the larger
than predicted values of scintillation which were observed with TACSAT
over the Pacific in the early 70 ' s . The occurrence of GHz
scintillation over the geomagnetic equator may be due to an additional
source (of outer scales) which is not easily observed from spectral
analysis at lower frequencies.
01 - 51
The bandwidth of scintillation is exceptionally broad and as a
result frequency diversity is not a practical possibility.
Polarization diversity is also found to be impractical as a mitigation
scheme. On the other hand, time diversity and space diversity hold
considerable promise. The space diversity concept operates on the
proposition that fading is independent if two ray trajectories are
sufficiently separated. Work at NOSC has shown that the minimum
separation is 700 to 1000 meters but is dependent upon the height of
the inhomogeneities or equivalent ly the Fresnel zone radius. Larger
spacings are required for periods of higher solar activity according to
the NOSC studies. This relatively significant receiver spacing
requirement to achieve diversity gain suggests that disadvantaged users
such as ships operating at low latitudes cannot be accomodated through
use of spaced antennas on the ship structure.
Time diversity schemes have been examined by several groups
including MIT/Lincoln Laboratory. Burst errors arising during
scintillation are randomized by interleaving, and convolutional
encoding is employed for forward error corrections. This procedure,
upon de-interleaving and decoding (Verterbi) , has been tested under
simulated Rayleigh fading conditions and appears to operate
successfully. However, it is an additional expense, and a sacrifice in
throughput and timeliness is imposed due to the delay in processing the
data (around 2 minutes) .
Remarks presented so far have been made in the framework of
amplitude scintillation effects, since very limited amounts of phase
scintillation data have been obtained upon which generalizations could
be based. This problem is being circumvented through use of recent
experiments aboard ATS-6 but most principally using transmissions from
WIDEBAND DNA-002. In these experiments, a UHF or GHz channel is used
as phase reference and differential phase data have been obtained at a
lower set of frequencies. Data of this type have also been obtained
using TRANSIT satellites and U.S. NAVY TIMATIONs (NTS 1 and 2).
Concern had been raised that PSK modulation schemes would suffer
additional degradation if phase scintillation were severe. Isolated
events have been reported which lend some credance to this fear.
However at the data rates employed by FLEETSATCOM, the COSTAS phase
lock loop in the standard receivers (viz, AN/SSR-1) typically responds
to the challenge so that phase scintillations may be ignored during
periods of low solar activity. During the more virulent periods of
activity in which inhomogeneities are in more rapid motion and fade
(and phase change) rates are enhanced, the matter is open at this time.
Statistical models of world-wide scintillation effects have been
constructed by workers at Stanford Research Institute using data
obtained principally at VHF, and localized empirical models have been
developed by a group at AFGL for both high and equatorward latitudes.
Since these models are statistical and subject to all the usual
D1 - 52
problems associated with attempts to represent complex (and poorly
understood or measured) phenomena with simple functions, they are not
particularly desirable for use in forecasting. Nevertheless they may
be used provided caution is observed.
A general review of all aspects of scintillation is being prepared
by the author of this note and will not be covered herein. We shall
presently concentrate only upon the solar and magnetic activity aspects
of UHF transmissions from a geostationary satellite.
2.0 Dependence of Scintillation on Solar Activity
As has already been noted, most evidence clearly points to the fact
that during epochs of higher solar activity a higher occurrence rate of
scintillation is to be expected. Furthermore in regions where the
occurrence rate is already high, the intensity of scintillation is
increased. In general both properties operate simultaneously except,
naturally, whenever amplitude scintillation is already saturated. Even
in this case the scintillation rate will be observed to increase.
Models have been developed which indicate the increase in
scintillation with solar activity both directly and indirectly (through
magnetic activity indices). Stanford Research Institute l-»2.,3.f
NOAA, *■ and AFGL 5. ,6., 7 nave published models and reviews have
been provided by a number of authors,*** »'« . it is noteworthy that
there are well over 300 papers which have been published by various
scientists dealing with various aspects of scintillation, and it would
be impossible to cite them here. However certain aspects of how the
sun controls scintillation have begun to emerge from detailed
morphological studies and modelling attempts.
The general view held is that solar activity enhances scintillation
over the equator, that magnetic activity enhances scintillation at high
latitudes and the auroral zone, and that midlatitude scintillation is
independent of both sources. Indeed the Fremouw-Pope-Rino Model (F-P-R
Model) as described by Fremouw et al *« expresses this view
analytically. The F-P-R model indicates:
S4 ~ S4 (Xm>T> + S4 <K>T>Kp> + S4 (Xm>T>y + S4 <K,\,1,»,X> <«
where S4 is the scintillation index
Xm is the geomagnetic latitude
Xg is the geographic latitude
D is the day of year
T is the local time of day
Kp is the planetary K index
R is the mean sunspot number
and the superscripts M, H, A, and E refer to
Midlatitude, High latitude, Auroral, and
Equatorial respectively.
D1 - 53
Figures 1-4 show how the S4 index appears for a sunspot number of
100 near vernal equinox at subsatellite local times of 0000, 0600,
1200, and 1800 hours using the model of Fremouw et al (F-P-R Model).
These graphics are intensity modulated (gray-scale) representations of
S4 for a transmitting synchronous satellite located at 75° W
longitude with the scaled values projected back to the geographical
positions of all surface points in view of the satellite. These
representations are for F-region scintillation only and are, of course,
only mean values. Nevertheless, they show the two principal
scintillation zones rather clearly.
It is worth mentioning again that solar and magnetic activity
dependencies are difficult to separate. Provided appropriate
solar-related observables are selected (not necessarily R but some
other parameter such as EUV, X-ray, or radio flux, solar wind velocity,
etc.) and suitable time constants are considered, it might be possible
to exclude Kp in future correlation analyses altogether (or
alternatively R if Kp is desired) . In this connection the F-P-R
model is observed to exclude a joint dependence upon Kp and R; this
is to avoid correcting for the same effect twice.
Let us now examine the predictions of the F-P-R model for a radio
frequency of 250 MHz and a sunspot number of 200. Figure 5 shows the
location of the four major communication area master stations (NAVCAMS)
on a grid in which a set of (300 kilometer altitude-referenced)
invariant latitude isopleths is overlaid and the zones of scintillation
are depicted. It would appear that we should consider the term
Sf (Xm,Xg, T, D, R) for Honolulu and Guam, S^(Xm ,T) for
Naples, and possibly S^( \m,T) and S§ ( Xm»T,Kp) for Norfolk.
Honolulu and Guam are roughly 20° and 10° above the geomagnetic
equator respectively. Evidence exists that equatorial scintillation
peaks at + 10° of the equator. It has a dependence above the equator
of the form^* :
(X - 10°)2 (2)
exp - m
(10°)2
A similar term exists south of the equator.
Hence S4 is maximized for Guam and reduced to g- at Honolulu; at
the equator itself S4 is equal to — of its maximum value because of
the sum of two terms.
Curves due to Fremouw et al *• for Ancon, Peru and Kwajalein
Atoll have been modified by the author of this paper to reflect a radio
frequency of 250 MHz and a sunspot number of 200. The original curves
were for f = 138 MHz and R = 21; translations in frequency for
amplitude and phase scintillation were
S. ~ f'1,5 (3)
4 f-i
0 rms ~
D1 - Sh
SCINTILLATION INDEX
TRANSMITTER
LATITUDE 0.00
LONGITUDE -75.00
ALTITUDE 40577.0 KM
FREQUENCY 254. 0 MHZ
WAVELENGTH 1. 18 METER
LOCAL TIME 0.5 HOURS
IONOSPHERE
ALTITUDE 350.0 KM
DEPTH 100.0 KM
AXIAL RATIO 10. 0
SUN SPOT NUM 100
DAY 81
YEAR
80-
60-
40-
- 80
- 60
- 40
-an
-a or
-0.11
-&2I
-4.28
-0.35
-0.12
-aw
-a si
-a«3
-aw
-an
-aw
-0.91
-a 98
-1.05
20-:
H °-
-20-
;- 20
- °E
■■:■— 20
-40-
—40
-60-
—60
-80-
1
in
1
i/i
(0
•-»
i
1
I I I I
ss p b g
i i i i
—80
I
in
Fig. 1
D1 - 55
SCINTILLATION INDEX
8371
TRANSMITTER
LATITUDE
LONGITUDE
ALTITUDE
FREQUENCY
WAVELENGTH
LOCAL TIME
0.00
-75. 00
40577. 0 KM
254.0 MHZ
1. 18 METER
6.0 HOURS
IONOSPHERE
ALTITUDE
DEPTH
AXIAL RATIO
SUN SPOT NUM
DAT
YEAR
350.0 KM
100.0 KM
10.0
100
81
K
80-
60-
40-
- 80
- 60
- 40
-0.00
-a or
-0.11
•0.21
•0.21
-0.35
-0.12
-aw
-a sb
-0.13
-0.70
-a 77
-0.M
-a»i
-a «8
-1.05
20-
H °-
-20-
- 20
- °E
—20
-40-
—40
-60-
—60
-80-
I
—80
1
in
1
1
in
1
in
IS)
t*i
Fig. 2
D1 - 56
SCINTILLATION TNDEX
TRANSMITTER
IONOSPHERE
LATITUDE
0.00
RLTITUOE
350.0 KM
LONGITUDE
-75.00
DEPTH
100.0 KM
RLTITUOE
40577.0 KM
RXIRL RATIO
10.0
FREQUENCY
254. 0 MHZ
SUN SPOT NUM
100
HOVELENCTH
1.18 METER
DAT
81
LOCRL TIME
11.8 HOURS
N
TEAR
in in
in in
10
in in in
in
m Pi
-< Ol
1
In n m
i i i
80-
60-
40-
- 80
- 60
- 40
-0.00
-0.07
;;-am
"-0.21
l-0b28
-0.35
J-0.42
-0.49
' -0.56
! -0.83
J-O.70
•-an
-0.94
-0.91
i-0.98
-1.05
20-
- 20
W M
- oE
-20-
—20
-40-
—40
-60-
—60
-80-
I
I
in
—80
Fig. 3
D1 - 57
SCINTILLATION INDEX
(OT)
TRANSMITTER
LATITUDE
0.00
LONGITUDE
-75. 00
ALTITUDE
40577.0
KM
FREQUENCY
254.0
MHZ
WAVELENGTH
1.18
METER
LOCAL TIME
18.3
HOURS
in in
in
in
in m
oi
IONOSPHERE
ALTITUDE
OEPTH
AXIAL RATIO
SUN SPOT NUM
DAT
TEAR
350.0 KM
100.0 KM
10. 0
100
81
80-
60-
40-
Bt!HtHhi..?^..,-..V.V.,.,V..'-l.|]i
v.,.,.,y,y,...
"' ^^^^itinbf!EBE;f.'E!HRR#^3 ^
- 80
- 60
- 40
-0.00
-0.07
,,-O.tl
;-0.21
J-0.J0
J-O.SS
J-o.w
J -0.19
J-0.S6
J-0.63
J-0.70
■-0.77
J-0.94
J-0.91
J-0.98
■-I.05
20-
N °-
-20-
-40-
—40
-60-
—60
-80-
—80
Fig. 4
D1 - 58
60 SO 0 SO 60
GEOGRAPHIC LONGITUDE (dtg)
Fig. 5 - Location of the Four Major NAVCOMSTAS with
respect to the regions of strong F-region
scintillation (shaded) .
«»y >coo— ><■
f- 250 MHz
R -=200
2O0
DAT
••roucxcr —
■'» moc« *i?8
JUN VOT
WJ JLOOWH.
J7S
J0»
117
f-250 MHz
R «200
uo
UO. 390
0 to
no
no - zoo
OAI
.OK)
7-.*n. i>t o.oo
I5"» lO«C nO 00
IM1I Ml 1U« ooo
'•lOUtMCT
U.90
2.00
«CvK tOK
Hey* hi
100 130
T5»r> utr aoo
TVulK L0"0 -O0U)
1WH b] luoo.ooo
6A
6B
Fig. 6A - Seasonal Dependence of Scintillation Index S4
during nocturnal hours (2200 local) for Kwajalein
Atoll and at a frequency of 250 MHz and for a
sunspot no. of R=200.
6B - RMS 0 scintillation (same conditions as A)
(Curves adapted from Ref 3)
D1 - 59
and translations in sunsDot numbers were made using the linear relation
3.
S, ~ <h ~ 1 + 0.04 R (4)
4 ' rms
which is applicable in the non-saturated regions. Figures 6 and 7 show
the projected seasonal variations in S4 and rms phase fluctuations
for Ancon and Kwajalein respectively. Figure 8 shows the diurnal
variation to be expected at Ancon at equinox. It has been shown
9. ,10. that if S4 £ 0.8 then the 1-99% fading range in dB is
approximately 19dB. This area is shaded. Under this condition the
FLTBCST channel of MARISAT/GAPFILLER will suffer a bit error rate
2: 10"-* and corrupted messages will occur^.
We see that corrupted messages will be observed on the average
every night £or sites similar to Ancon and Kwajalein except during
local wintertime. Furthermore it will persist for approximately six (6)
hours. It is odd that the APL report-^ • does not allow for any
appreciable solar activity effect.
Figure 9 is a NOSC prediction of the magnitude of equatorial
scintillations to be expected at sunspot maxiumum. Their assertion of
a projected 30% occurrence of scintillations ( ~ 7.5 hours/day for
worst month conditions and S4 y 0.3 or fading ^ 6dB) is somewhat
lower than the 42% occurrence (i.e. ~ 10 hours/day for S4 ^ 0.3)
implied by Figure 8. Furthermore Ancon is virtually on the magnetic
equator and would be subject to somewhat less intense scintillation
than that observed at GUAM because of relation 2 above (by a factor
of -2 or 1.4dB) . In sum, the F-P-R model predicts that equatorial
scintillation for sites like Guam will be greater than or equal to
~ 20dB (based upon Ancon projections) 6 hours/day on the average for
the worst month case. Further, at least 1 hour/day of scintillation
% 20dB willbe observed for 60% of the year (i.e. all year excluding
the period near local winter). Scintillation is reduced by 4.4dB on
the average at Honolulu.
Scintillation at Naples, which is strictly in the midlatitude zone,
should not be particularly severe except possibly during local summer
when sporadic E ionization is enhanced. The probability of sporadic
E-induced ionization has been examined recently by the author^,
based on earlier work at VHF^..
Scintillation at Norfolk may be severe during nocturnal hours
following magnetic storms. This is due to the southward expansion of
the equatorward edge of the scintillation boundary. There is little
data presently available to provide a projection for large solar
activity epochs. However the occurrence of major magnetic storms is
known to be related to the occurrence of large solar flares and
enhancements in solar wind velocity. Scintillation, as observed from
Washington, D.C., following magnetic storms has been reported both at
VHF and UHF14*'1-5*. Projections of difficulty in interpretations of
D1 - 60
7A
f-250 MHz
R -200
Local
Winter
V
200
0»»
«» IMEXI
Sun VW
is
«CV» l»t
7B
250 MHz
■200
Local
Winter
-IIJ* T5MT« L»T 0.00 "fOuCMCT
■n,ij !> .>« lc~o i.o.w 1-uS
M ij-i! M° ltioS.'So
»cvn LAT .n.7» 1WK UIT 0.00
Mv« L0NS -n.lS IV'TD IOM0 -110.00
Kit Hi JO*% 1S-I« Hi IMOO.OOO
Fig. 7A - Seasonal Dependence of Scintillation Index S4 during
Nocturnal Hours (2200 Local) for Ancon, Peru and at
a frequency of 250 MHz and for a sunspot No. of R=200.
7B - RMS 0 scintillation. (same conditions as A)
(Curves adapted from Ref 3)
8A
l«u(
«» "«0f«
f- 2 50 MHz
R -200
BQUINOX
-II.H TSUTa L»T 0.00
J>?» tuIk «v^ ittoo.Ko
f- 250 MHZ
R -200
">fOUtMCT
YiMC vaaiaOl/
«» INOfl T.I
Iff"*'
8B
Fig. 8A - Diurnal Variations of S4 Index for Ancon, Peru for
f=250 MHz and R=200.
8B - Diurnal Variations of RMS 0 for Ancon, Peru for f=250MHz
and R=200.
D1 - 61
Fig. 9A
Observed and Predicted Solar Activity Indices (Sunspot No.)
from 1740. Absolute values of the extrema are to be
interpreted as the peak sunepot numbers. The smooth curve
(prediction) near 1981 is seen to be as large as the 1959
peak, the largest in recorded history. (Ref 16)
msut^ii mo hoicto unn man
9B
Detailed plot of solar cycle 21 predictions. (Ref 16)
9C
30
z
,9 20
32
0
n ' » 100 Of DATA • U HP TO 4 OCT EACH T( AK
PREDICTED PEAK 1981-
1
i
-
SUN SPOT yS
NUMBER ■^^^S'
1970 yS
i
i
i
1
l
i
i
1971 .
/C1976
•''01972
I
1
i
1
i
i
100 200
SUN SPOT NUMBER (ELEVEN DAY AVERAGES)
Predicted Scintillation at 250 MHz for GUAM at equinox
(Ref 16) (Also from several papers by R.U.F. HopVins at NOSC)
D1 - 62
FLTBCST messages at solar maximum in the Norfolk area roughly
translates to projecting the number of major magnetic storms. This is
a difficult and risky business.
Scintillation at high latitudes is slightly less severe than that
over the equator but is essentially omni-present , exhibiting little
variation with season or time of day at fixed invariant latitudes and
fixed values of Kp. However the auroral oval (and scintillation
boundary) sweeps out different geographic latitudes as a function of
time and as a result a ship positioned at a fixed high latitude point
will observe a diurnal dependence of scintillation. At operationally
important oceanic regions between Greenland, Iceland, and the United
Kingdom (termed GIUK gap), for example, scintillation will be enhanced
during the night and least (but not zero) during the dayl^*. Ships
in the North Atlantic will be particularly vulnerable to scintillation
following magnetic storms, even during daytime hours due to the
southward movement of the various circumpolar features.
3.0 Resume of U.S. Navy Position Vis-A-Vis Scintillation
The U.S. Navy is now considering various options for mitigation of
UHF scintillation, specifically for fleet broadcast (FLTBCST) channels
and these are presently being considered from a broad systems
viewpoint. The various techniques are typically evaluated with due
consideration for whether the Fleet asset is either a ship or a ground
station. As would be expected, space diversity is only applicable to
the FLTBCST downlink to the communication area master stations (CAMS)
since considerable real estate is required. As a result its
incorporation will not generally be of service to the Fleet except as a
monitoring system. The use of time diversity schemes (interleaving and
forward error correction) is useful for both uplink protection from the
CAMS and downlink to the ships or the CAMS, provided special decoding
and de-interleaving equipment is available. However, it is generally
concluded that coding schemes cannot be practicably employed for high
data rate (2400 BPS) channels in a polled net or in Demand Assigned
Multiple Access (DAMA) scenarios. These systems are also quite
expensive. Brute force techniques such as increasing uplink effective
isotropic radiated power (EIRP) or downlink shore G/T are also being
explored; these options are also not without drawbacks.
One of the more viable long terra possibilities is to avoid UHF
scintillation altogether by inserting FLTBCST into the SHF channels of
future synchronous satellite systems such as FLTSATCOM or LEASAT. This
option will require acquisition of SHF receiving equipment by the Fleet
and such plans are now being formulated. However, these plans will not
be brought to fruition during the 1980 to 83 epoch during which time
scintillation may be at its peak levels. In summary, the downlink
protection for ships against scintillation is less than complete, and
there is no short term solution to this problem. The intermediate
solution involves protection of links to major flag ships and carriers
D1 - 63
using SHF equipment. A short term solution for the more critical
circuits located at the CAMS might involve several options not the
least of which is SHF relay of FLTBCST to an alternate site using the
Defense Satellite Communications System (DSCS) channels. This
alternate site, hopefully being located in a non-scintillation region,
would copy UHF FLTBCST from FLTSATCOM and would retransmit the traffic
to the CAMS via the relatively non-vulnerable DSCS links at 7-8 GHz.
The role of forecasting and prediction of scintillation would
appear therefore to be of some practical interest in resource
management in the near term and may extend into the intermediate and
long terms .
4.0 Summary
We have shown in this brief note that scintillation effects at UHF
(250 MHz) have the potential to be extremely deleterious during the
upcoming epoch of solar activity, predicted to be as high as 200 (See
Figure 9) . 15-
This is a preliminary assessment. Work is continuing to refine the
estimates.
The author would like to thank LCDR Claude LaVarre, Dep. Director
Naval Electromagnetic Spectrum Center, Naval Communications Unit, for
suggesting this topic. LCDR C. French of NAVELEX is acknowledged for
his comments and Dr. E. Fremouw made several helpful suggestions in
reviewing this paper.
REFERENCES
1. Fremouw, E. J. and C. L. Rino, 1973, Radio Sci. 8, 213.
2. Rino, C. L. , E. J. Fremouw, A. R. Hessing, and V. E. Hatfield,
1978, RADC-TR-78-87.
3. Fremouw, E. J., C. L. Rino, A. R. Hessing, and V. E. Hatfield,
1978, RADC-TR-78-88.
4. Pope, J. H., 1974, NOAA TR ERL 308-SEL 30.
5. Aarons, J., J. Muller, H. Whitney, E. Martin, K. Bhavnani, L.
Whelan, 1976, AFGL-TR-76-0210.
6. Basu, Sunanda, Santimay Basu, B.R. Khan, 1976, AFGL-TR-7 6-0080.
7. Aarons, J., E. MacKenzie, and K. Bhavnani, 1978, Proc. AGARD NATO
Specialists Conference, Ottowa, Canada, (papers 5-1) .
8. Aarons, J., 1976, AFGL-TR-76-0078 .
9. Crane, R. K. , 1974, MIT Lincoln Lab Report 1974-29.
10. Goodman, J. M. , P.L. Watkins, C.G. Myers, R. Hogg, 1978, NRL
Report 8160
11. , 1976, Johns Hopkins APL, SDO-4380.6
12. Goodman, J.M. , 1976, NRL Memo Report 3396
13. Goodman, J.M., 1967, J. Atmospheric Terrest. Phys. 29, 607
14. Goodman, J.M. , 1968, J. Planet. Space Sci. 16, 951
15. Goodman, J.M. , R. Zirm, R. Beard, 1978, URSI Proc. Helsinki
16. Argo, P.E., and J. R. Hill, 1978, IES'78 Proc, paper 5-1
D1 - 6*4
IONOSPHERIC REFRACTIVE CORRECTION USING AN ADAPTIVE PROCEDURE
D.E. Donatelli
Regis College Research Center
Weston, Massachusetts
R.S. Allen
Air Force Geophysics Laboratory
Hanscom AFB, Mass. 01731
The time and space variability of the ionosphere as it impacts
range correction for radar, navigation and communication systems
is considered. An adaptive technique for reducing this impact is
examined using TEC data from locations representative of the extent
of a typical radar coverage area. Results indicate the procedure
is successful during periods when the absolute residual error in
range correction is maximum.
INTRODUCTION
Radar, navigation and communication systems are able to achieve greater
precision through advancements in technology, but daily variability of the
ionosphere constrains achievement of their desired accuracy. Numerical maps
which provide monthly median corrections have been derived from a world-wide
climatology of ionospheric parameters; their use alone reduces the residual
in range or time delay measurements to about 20 - 25 percent of the median
correction in day time and 30 - 35 percent at night. It is this residual
which proposed adaptive techniques attempt to reduce.
Here we will examine the results of using a scaling procedure with a
numerical map of median correction within a radar coverage area. The scaling
is obtained from real-time measurements of total electron content (TEC) com-
pared with the median TEC for the time and location of the measurement. The
refractive correction, which is directly proportional to the electron con-
tent along the ray path, is then scaled by this factor. Both temporal and
spatial growth of residual error is examined. The zero-point of error is set
by the time and place of calibration; the maximum, by the time-space interval
required to achieve the magnitude of the median residual error. This inter-
val, and the magnitude of the error within it, determines the effectiveness
of the procedure.
D1 - 65
2 . PROCEDURE
For an operational-type assessment of this procedure, a radar location
is hypothesized in the central U.S. Its coverage area is represented in
Figure 1. The locations marked are the subionospheric points for stations at
which TEC archive data were available. Those marked "x" had simultaneous
data for the 1968-69 solar maximum; those marked "o" for the 1974-76 solar
minimum. Data from Hamilton, Mass. (HAM) were available for the entire 1968-
76 period, and from Goose Bay, Labrador (GSB) for 1972-76. The TEC data are
reduced measurements of Faraday rotation of the VHF beacons from the geosta-
tionary satellites (Titheridge, 1972): ATS-3 for Hamilton, Goose Bay, Kennedy
Space Flight Center, Florida (KSF) , Urbana, Illinois (URB) ; ATS-1 for Stanford,
California (STA) , Edmonton, Alberta (EDM) . The entire set of HAM data were
used to examine the temporal variability over season and solar cycle (DuLong,
1977) and the GSB data were used for a comparison of results at two locations
(Donatelli and Allen, 1978).
To initiate the procedure, a real time observation is obtained from one
of the data stations. The calibration consists of a scaling factor determin-
ed by comparing the observation with the expected median. This factor is
used to scale the median at 15-minute intervals throughout the day. Figure 2
demonstrates this procedure with calibration occurring every 2 hours, on the
hour, for the case where the calibration is made along the same ray path to
which the adaptive procedure is applied. Each curve originating at the cal-
ibration time demonstrates the average effect over the month of using the
scaling factor from this time for 12 succeeding hours. It is obvious that
the maximum time interval for which a scaling factor is useful, or, at least,
not detrimental, is bound by the time of calibration on one end and the suc-
ceeding solar terminator on the other.
TIME VARIABILITY
A summary of the HAM data study is provided in Table I, representing the
solar maximum conditions, S =_155, R =110, and the solar minimum conditions,
S = 71, R =10, where S and R represent the twelve-month running mean solar
flux at 2800 Mhz and sunspot number, respectively. The values, in meters, of
the parameters for range correction and the residual errors are listed at the
local times of the daily mean maxima and minima for the periods representing
the seasonal maxima and minima, in simulation of actual use by a 425 Mhz rad-
o
ar on a target at 1000 km altitude, 5 elevation angle. To estimate the range
correction for other values of S it is possible to interpolate or extrapolate
to a reasonable approximation by assuming a linear relationship between S and
TEC.
D) - 66
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The parameters listed are:
AR -the ionospheric component of range measurement
6R
m
6R
3h
6R
lh
6R
30m
-the residual error in range correction using a median prediction,
caused by the day-to-day variability of the ionosphere
-the residual error in range correction using a scaled median
prediction three hours after updating
-the residual error in range correction using a scaled median
prediction one hour after updating
-the residual error in range correction using a scaled median
prediction thirty minutes after updating
TABLE I
WINTER
VERNAL
EQUINOX
SUMMER
AUTUMNAL
EQUINOX
MAX
MIN
MAX
MIN
MAX
MIN
MAX
MIN
AR
6R
m
6R
3h
6R
6R
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AR
6R
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6R
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6R
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6R
Solar Maximum (R = 110; S = 155)
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D1 - 69
This table shows that an updated prediction of median range correction can
reduce the residual error by 60 percent after one hour, and by 30 percent in
daytime at solar maximum even after three hours. It appears that at solar
maximum there are large amplitude long period variations that are readily cor-
rected with updating. Shorter period smaller amplitude fluctuations super-
imposed on these, exist at both solar maximum and minimum and impose a limit
on effectiveness.
Near sunrise and sunset and during severe magnetic disturbances, periods
of rapid changes in TEC, the same degree of reduction in error can be main-
tained by reducing the interval for updating to about 15 - 30 minutes. This
is demonstrated in Figure 3, using the adaptive procedure on a highly dis-
turbed day. Calibration in 30-minute intervals would allow a 65 percent re-
duction in the maximum error of the day despite the steep gradients in TEC.
The comparison of HAM results with those for the same procedure applied
at GSB is presented in Figure 4 using the parameters as defined in Table I,
with the addition of:
5R- r -the residual error in range correction using a scaled
15m , . . r . r . r i
prediction fifteen minutes after updating
The curves are comprised of the maximum value each month of the designated
parameter. The results are similar for both stations, indicating the lati-
tude variation, in this case, may not be significant in day time when the
maxima occur.
It must be emphasized that the time interval for effective updating is
determined by the rate of change of TEC. Since these data are reduced at 15-
minute intervals, fluctuations with a period less than 30 minutes are not ob-
servable. The amplitude of these is assumed to be much smaller than the mon-
thly average variability. Therefore, it is the effects of the longer period,
and presumably larger amplitude, variations that are being reduced here. The
amplitude of the shorter period variations determine the limits for minimi-
zing residual error.
During sunrise and sunset periods, the effects of production and loss,
respectively, create gradients that dominate all other fluctuations. Similar
gradients may occur during magnetic disturbance. There may be large rapid
variations, particularly in the region of the auroral zone and the trough in
high and mid-latitudes. It is the rate at which these changes occur that
must set the calibration interval at these times.
4. TIME - SPACE VARIATION
Time and space variations cannot be viewed independently. Even if a
calibration is used instantaneously, there are likely to be local time var-
iations, for at any longitude, actual sun time varies over latitude, except
briefly at the equinoxes. Therefore, any spatial variation includes temporal
effects. Spatial variations have been examined in previous work (Allen, 1977;
Leitinger et al, 1978) using data from the TRANSIT satellites reduced to pro-
vide TEC along the satellite path. The variation of ionospheric features and
some of the implications of attempting to track these features in space and
time were examined, and the conclusions are confirmed by this present study.
The work discussed up to this point assumes the adaptive procedure
D1 - 70
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8 10 12 14
LOCAL TIME
16 18 20 22 24
The effectiveness of an updating procedure during a severe magnet-
ic disturbance, comparing the actual required range correction,
ARd, with the predicted median, AR, and the 30 minute, Ar30 m>
and 3 hour, AR3 h» updated predictions. The differences in the
range correction curves of the upper scale are presented as
absolute error on the lower scale.
D1 - 71
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72
would be applied along the same path as the observation. In actual use this
would occur rarely. A valid assessment of an adaptive procedure requires
examination of error growth across a region comparable to a system coverage
area. The stations shown in Figure 1 provide the best available data for
this purpose.
Data availability required that the procedure be examined in two seg-
ments: the 68-69 solar maximum period data from HAM, URB, STA AND EDM; and
the 74-76 solar minimum period data from GSB, HAM AND KSF. The first segment
includes longitudinal variations between the station pairs HAM-URB and URB-
STA, and primarily latitudinal effects between EDM-STA. For the second seg-
ment, latitudinal effects dominated the station pairs GSB-HAM and HAM-KSF.
Preliminary results, presented in Figures 5-7 show that the degree of
success (or failure) of the adaptive procedure depends on the difference in
the percentage variability along the ray path used for calibration and the
ray path of the applied correction. The upper two sets of curves compare the
means and the standard deviations, respectively, for the station pair. Fig-
ure 5 is the Stanford-Edmonton pair for the 1969 April and October equinox
months and Figure 6, the Stanf ord-Urbana pair for the same period, showing
latitude and longitude effects, respectively. Figure 7 is the Goose Bay-Ham-
ilton pair for the same months, but near solar minimum, 1975. The latitudi-
nal extent is similar to Stanford-Edmonton. The standard deviation repre-
sents the variability at each station; the comparative percentage variability
can be determined from the differences between the mean and standard devia-
tion (6Rm) curves for each station. If there is a large difference in the
Percentage variability between the two stations, the one with the lesser is
preferred for calibrating. It should also be noted that the night time var-
iability often differs considerably between stations and this may be attri-
buted, in part, to conjugate effects.
In applying the adaptive procedure a calibration at one station is used
to determine the factor to update the mean of the other. The process is
applied reciprocally between each pair of stations. The lower two sets of
curves compare 6R™ at the station which is being updated, with the residual
error when the adaptive procedure is applied 15 minutes (<5Rl5m) and 3 hours
(6R3h) after calibration. Thus, the set labeled EDM -> STA, in Figure 5,
implies that the calibration was made at Edmonton and the adaptive procedure
was applied at Stanford; vice-versa for STA-*EDM; similarly for URB->STA and
STA-HJRB in Figure 6, and GSB-HAM AND HAM-GSB for Figure 7. At solar maximum
<5Rl5m and 6R3h are comparable indicating that the residual error can be ef-
fectively reduced after 3 hours in daytime. Note that the implied local time
difference in the STA->URB 8R2h curve is approximately 6 hours, but the resid-
ual error is comparable to 6Ri5m which is a 3-hour local time variation,
thus, inferring that the correction is for large scale spatial, not temporal
effects. This result does not apply at solar minimum however, as Figure 7
shows. The curve for residual error when the adaptive procedure is applied
one hour after calibration (6Rlh) is included here to emphasize that at solar
minimum a measurement can be used for about one hour. Unlike the solar max-
imum period, the residual error continues to increase to the degree that 6R3h
is comparable to 6Rm, implying it may be preferable to revert to a median
correction after one hour if a new calibration is not available. This is
consistent with results presented in the section on time-variability.
The diagram of Figure 8 shows the relative location of station pairs as
difference in degrees latitude from South to North and from West to East
D1 - 73
APRIL 1969
OCTOBER 1969
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Figure 5. The mean and standard deviations are compared to determine the
relative percentage variability for the Stanford-Edmonton station
pair in the upper two sets of curves. The lower two sets compare
the results of applying the adaptive procedure at each station
using 15-minute and 3-hour calibration intervals in April and
October 1969.
D1 - Ik
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Figure 6. Same as Figure 5, but comparing the Stanf ord-Urbana station pair
D1 - 75
APRIL 1975
OCTOBER 1975
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Figure 7. Same as Figure 5 but comparing the Goose Bay-Hamilton station pair
for April and October 1975, also including the results for a
1-hour calibration interval.
D1 - 76
longitude. The STA-EDM and KSF-HAM pairs have the greatest latitude separa-
tion while STA-URB has the greatest separation in longitude. The effects of
these latitude and longitude differences are illustrated in Figure 9 where
the stations Stanford, Urbana and Hamilton are used to represent target loca-
tions. The curves demonstrate the dependence of residual error on the ray
path used for calibration in the adaptive procedure: the 6Rm are again the
standard deviation at the station for the month of October; the 6Rjr , SR^h,
6R3h are for the time interval of applied update as in previous figures, but
here they represent calibration along the ray path to the target. Each of
the two curves labelled 6R, with a station name, is the 15-minute applied
update with calibration from that station, both from different directions.
In Figure 9a, SRjjRB an<^ <5ReDM give results comparable to 6R3h, with
6ReDm producing better night time and 6Rjjrb better day time results. A 50.
percent reduction is possible in day time in both cases.
With only a few degrees variation in latitude but a large longitudinal
variation, the time-space equivalence in longitude becomes apparent. In
Figure 9b, 6RsTA» which includes a 2 hour 45 min local time difference, is
comparable to <5R3h> while 6RhaM> with a 1 hour local time difference, com-
pares with the 6Rih' The differences in results using different ray paths
represent spatially localized uncorrelated variations as shown by Davies et
al, 1978.
In the case of equal degree-longitude separation but unequal degree-
latitude separation as in Figure 9c, 6RqsB and 6RkSF are comparable to ^R^Yx
as is <5Redm of Figure 9a. The calibrations are from opposing directions
with <5Rqc]3 producing better day time results than 6R^SF which includes a
greater latitude distance. The nighttime results are poor in either case,
with SRgsb the worse, perhaps because of its proximity to the auroral zone.
A lower limit to the residual error is represented by ^R^ for each
target location in Figures 9a, b and c. This is set by the amplitude of
daily variations with a period less than 30 minutes
5. DISCUSSION
In the procedure examined here a simple scaling method was used to
reduce the residual error in ionospheric correction that exists because of
daily variability about the mean behavior. This scheme is most successful
when the scaling factor is determined, and the update applied, along the same
ray path. This is generally not the case, however, and problems arise when
the variability differs considerably across a system coverage area. A
greater spatial incoherence is found in latitudinal separation as opposed to
longitudinal separation as has been shown previously in correlation studies
using TEC and foF2 (Klobuchar and Johanson, 1977; C. Rush, 1976). At solar
maximum the large scale, long period variations predominate, while at solar
minimum it is the smaller s;ale, shorter term variations that contribute to
the greater percentage of the daily variability. These are less likely to
be correlated over large distances. The possible causes of consistent
differences in variability need to be understood in order to develop a
weighting scheme to compensate for them. In determining the space-time
interval for this adaptive correction scheme the important factors are:
location of the terminators, frequency and scale size of large amplitude
D1 - 77
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D1 - 79
fluctuations and their rate of change in time and space define the boundary
of the calibration intervals with precedence given to the terminators. Dur-
ing sunrise, sunset and magnetic disturbances these intervals may be as short
as 15-30 minutes of time and space equivalence. At solar minimum a signifi-
cant reduction may require a one hour interval while at solar maximum a
comparable percentage reduction in residual error is possible using a 3-hour
interval.
6 . ACKNOWLEDGEMENTS
The authors would like to thank Mr. J. Klobuchar of AFGL for the use of
the TEC data and for many helpful suggestions.
This work was supported by Air Force Contract F 19628-76-C-0255 .
REFERENCES
Allen, R.S. (1977): Considerations Relative to Adapting TRANSIT Observations
to Predicting Radar Range Corrections. AFGL-TR-7 7-0004 , DDC# ADA
038238.
Davies, K. , W. Degenhardt, G.K. Hartmann, R. Leitinger (1978): Electron
Content Measurements over the U.S. Joint Radio Beacon Program NOAA/MPAE/
GRAZ, Station Report ATS-6° W.
Donatelli, D.E. and R.S. Allen (1978): Temporal Variability of Ionospheric
Refraction Correction. Effect of the Ionosphere on Space and Terrestial
Systems, Editor J.M. Goodman, January 1978: 490-496.
DuLong, D.D. (1977): Reduction of the Uncertainty of Radar Range Correction.
AFGL-TR-77-0125, DDC# ADA 046166.
Klobuchar, J. A. and J.M. Johanson (1977): Correlation Distance of Mean
Daytime Electron Content. AFGL-TR-77-0185 , DDC// ADA 048117.
Leitinger, R. , R.S. Allen, D.E. Donatelli, G.K. Hartmann (1978): Adaptive
Mapping of Ionospheric Features. Effect of the Ionosphere on Space and
Terrestrial Systems, Editor J.M. Goodman, January 1978: 530-537.
Rush, CM. (1976): An Ionospheric Observation Network for use in Short-Term
Propagation Predictions. Telecommunication Journal, 43 (VIII): 544-549.
Titheridge, J.E. (1972): Determination of Ionospheric Electron Content from
the Faraday Rotation of Geostationary Satellite Signals. Planetary and
Space Science, 20: 353-369.
Dl - 80
PREDICTION OF TRANSIONOSPHERIC SIGNAL TIME DELAYS AT
WIDELY SEPARATE LOCATIONS USING CORRELATIVE TECHNIQUES
HAIM SOICHER
COMMUNICATIONS SYSTEMS CENTER
US ARMY COMMUNICATIONS R&D COMMAND
FORT MONMOUTH, NJ 07703
Excess time delays of transionospheric radio signals
introduce ranging errors in satellite-navigation and radar
systems, which are directly proportional to the total electron
content (TEC) along the propagation path. Correlations of TEC
values (based on linear regression analysis) at Fort Monmouth,
NJ (40.18°N, 7A.06°W) and Richmond, FL (25.60°N, 80.40°W),
as well as at Richmond, FL and Anchorage, AK (61.04°N, 1A9.75°W)
were previously determined. The correlation analysis was
performed at monthly and daily intervals for winter periods
during the quiet phase of the solar cycle.
Average regression lines obtained by the analysis were
then used to try to determine TEC at Richmond, assuming the
availability of TEC in Fort Monmouth, and at Anchorage,
assuming the availability of TEC at Richmond. In most cases,
the "predicted" TEC was within one standard deviation of
actual observed data for the former case, and within two
standard deviations for the latter case.
INTRODUCTION
The effects of the ionization along the satellite-to-ground signal-ray-
path on the propagation time of such a signal was previously discussed.
(Soicher, 1977). The excess time delay introduced by the ionization is
directly proportional to the total electron content (TEC) along the
signal path. In view of the stringent accuracy requirement of modern
satellite-navigation and radar systems, the excess time delay must be
compensated for either by real time measurements or through empirical
modeling techniques. The former requires that the user possess dual
frequency reception capabilities, while the latter (which utilizes a
single frequency) depends on how well TEC and its temporal and spatial
variability can be modeled and/or predicted. For improved accuracy,
the forecasting techniques should be supported by periodic updating of
data (preferably in real time) at specified locations. The question
arises as to the extent of the geographic area, surrounding a station
D1 - 81
having real-time TEC-determination capabilities, within which TEC values
could be interpolated with acceptable accuracy. In other words, could
TEC be determined at Location A if a real-time measurement was taken at a
different location, B, and what would be the geographic constraints of
A and B?
To this end, a specific investigation designed to determine the
correlation (based on linear regression analysis) between TEC values at
Fort Monmouth, NJ (40.18°N, 74.06°W) and at Richmond, Florida (25.60°N,
80.40°W) (Soicher, 1978a), and between TEC values at Richmond, Florida
and Anchorage, Alaska (61,04°N, 149.75°W) (Soicher, 1979) was undertaken.
Beacon transmissions from geostationary satellites were used to determine
the TEC at the stations by means of the Faraday rotation technique.
The sub ionospheric points for the Richmond-Fort Monmouth stations
(i.e., the geographic locations where the ray paths to the ATS-6 (located
at 94°W) intersect a "mean" altitude of 420 Km) were 36.5°N, 76.6°W, and
23.6°N, 81.6°W, respectively. Thus, the "representative" TEC for the two
stations was separated by /s/13° in latitude and by * 5° in longitude
corresponding to a 20- minute difference in local time) . The subiono-
spheric points for the Richmond-Anchorage monitoring the SMSI (located at
105°W), and the ATS-6 (located at 140°W) , respectively, were 22.5°N,
82.7°W and 54.3°N, 147. 3°W respectively. The "representative" TEC was
separated by * 31.8° in latitude and /v63.8° in longitude (corresponding
to a 4 hr 15 minute difference in local time) .
The correlation data indicated that TEC, or equivalently, ionospheric
signal time-delays, are highly correla table at the two sets of locations.
When daily data sets were compared at approximately the same local time
the correlation coefficients were, in general, £0.9 for the Fort
Monmouth-Richmond locales, and >, 0.7 for the Richmond -Anchor age locales.
The next phase of the investigation was the effort to determine
whether it is possible to accurately predict TEC at one locale from TEC
at the other, using average regression lines obtained for the correspond-
ing data sets. The technique employed was as follows: Average monthly
regression lines were computed. In one case, average slopes as well a
average intercepts of the regression lines at monthly intervals were
computed. In a second case, average slopes were computed while the
intercepts were forced to pass through a common data point for the two
sets at a specific predawn time for each day. Having determined the
average regression lines, TEC at one locale was calculated for a given
TEC at the corresponding other locale. The deviation (D-^) of the
calculated TEC from its actual value at a particular time is then
determined. This deviation, D^ is then divided by <T^ , the monthly TEC
standard deviation value at the same time. The average absolute value
of this ratio, i.e., |D_| was then computed for each day.
T
The results for the Fort Monmouth-Richmond data sets (i.e., predict-
ing TEC at Richmond from TEC at Fort Monmouth) using average slopes and
intercepts of the monthly regression lines are shown in Fig. 1. The
results for the Richmond-Anchorage data sets (i.e., predicting TEC at
D1 - 82
Anchorage from TEC at Richmond for the same local time) using average
slopes and intercepts of the monthly regression lines are shown in Fig. 2.
DISCUSSION
N I I
As Fig. 1 indicates, the daily average of the ratios JJ)J ^ *_ *S '£iJ
<r'H £,«";
N < 96 for Richmond is, for the most part, smaller than one, i.e., on the
average, the deviation of the computed Richmond TEC values from Fort
Monmouth TEC values is, in general, within the monthly standard deviation
of the Richmond data. The. diurnal behavior of the ratio is such that the
ratio is higher during the night (when tf" is small) than during the day.
Some of the high values of this ratio are attributable to ionospheric
effects during magnetically active period, e.g., on September 15 and 18,
1974, large enhancement of TEC were observed in response to magnetic
sudden commencements; on March 11, the Kp index ranged from 4° to 7".
The results of the figure also indicate that the ratio appears larger
during the equinoctial period (September, March) than during the winter
and spring months. This is observed despite the fact that the standard
deviation during the equinoctial months v/as considerably higher than
during the other months. The ratio, in general, does not change substan-
tially (as compared to the above case) when the average regression slopes
are forced to pass through the actual data points at the two locations
at specific time. (Soicher 1978b).
As Fig. 2 indicates, the daily average of the ratios |D(/p for
Anchorage is for the most part, smaller than two, i.e., on the average,
the deviation of the computed Anchorage TEC values from the corresponding
Riclimond TEC values, is, in general, within two standard deviations of the
Anchorage data. As in the Fort Monmouth-Richmond data sets the diurnal
behavior of the ratio is such that the ratio is higher during the night
than during the day. In addition, the figure indicates that the ratio is
larger on the average in October than in the following two months. This
occurs despite the fact that the correlation coefficient was, on the
average, higher in October, declined in November and declined further in
December (due to changes in TEC diurnal shapes associated with changing
separation in sunrise and sunset times at the two locales) (Soicher 1979).
As with the Fort-Monmouth case, the ratio here does not change substanti-
ally (as compared to the above case) when the average regression lines are
forced to pass through the actual data points at the two locations.
Since total signal time-delays are largest during the day and thus,
introduce significant errors in navigation and radar systems, it is
appropriate to examine the ratio \T>V(T during the time when TEC is
diurnally larger, i.e., between 1500 and 2100 UT (Richmond, Fort Monmouth
times and corresponding Anchorage time) .
For the Fort Monmouth case the data indicates that the ratio )d)/<t
obtained by average regression lines computed by the two techniques for
the day period, are substantially lower than the corresponding ratios for
the full diurnal periods. The fact that the bulk of the data indicates
that the ratio falls below 1 is encouraging since both correlation
Dl - 83
1750 0-
1500
1 250 -
1000 -
750 -
500
.250 \
0 \-
'• PREDICTIONS BASED ON AVERAGE REGRESSION LINES-
las oin-i77o<>n RICHMOND.PLA (PULL TIME INTERVAL)
185 210 ITi 220 201
t t t t
230
t
t t t
245 290 217
192
213
t
5 15 25 I 5 15 25 I 5 15 251 5 15 25 I 5 15 25 I 5 15 25 I
3EPT-74 JAN-75 PEB-75 MAR-75 APR-75 MAY-75
DATE
FIG. 1. THE VARIATION OF THE RATIO IdI/^FOR RICHMOND, FLORIDA, FOR THE
TIME PERIOD SEPTEMBER 1974, AND JANUARY 1975-MAY 1975, CALCULATED FOR FULL
DIURNAL PERIODS BY AVERAGE REGRESSION LINES OBTAINED BY FORT MONMOUTH, NJ-
RICHMOND, FLORIDA DATA SETS. ( |D| = DIURNAL AVERAGE OF THE DEVIATIONS OF
THE COMPUTED TEC VALUES FROM OBSERVED ONES;0-= MONTHLY STANDARD DEVIATION
OF THE RICHMOND DATA). THE ARROWS AND THE CORRESPONDING NUMERICAL VALUES
ARE FOR THOSE VALUES OF THE RATIO WHICH EXCEED THE SCALE OF THE FIGURE.
ALSO INDICATED IN THE UPPER PORTION OF THE FIGURE ARE THE NUMBER OF TEC
DATA PAIRS AT 15-MINUTE INTERVALS USED IN THE ANALYSIS.
« 100
a.
o
0
<= 2.0
1 5
10
5
PREDICTIONS BASED ON AVERAGE REGRESSION LINES
ANCHORAGE. ALASKA FULL TIME INTERVAL)
S °> »
o
*N
r-in
t
,C"4
M
3S6
10 15 20 25
OCTOBER 1976
5 10 15 20 25 30
NOVEMBER 1976
10 15 20 25 30
DECEMBER 1976
FIG. 2. THE VARIATION OF THE RATIO
|D|/«
DATE
FOR ANCHORAGE, ALASKA, FOR THE
TIME PERIOD OCTOBER 1976-DECEMBER 1976, CALCULATED FOR FULL DIURNAL PERIODS
BY AVERAGE REGRESSION LINES OBTAINED BY RICHMOND, FLORID A- ANCHORAGE,
ALASKA DATA SETS.
3^4
methods yield "predicted" TEC values that fall within the monthly standard
deviation of the data during the time period when the presence of TEC poses
the source of largest error.
For the Richmond-Anchorage case a similar statement cannot be made.
On the average, the ratio is not markedly different for the full time
interval and for the time interval for maximum values of TEC.
CONCLUSIONS
The high correction of signal time delay variation at two sets of
locale separations, one widely separated by latitude, and the other widely
separated by latitude and longitude (and hence by local time) , prompted
the examination as to whether time-delay data at one locale may be
"predicted" if continuous corresponding data were available at the other
locale. The correlation is high, in part, due to the 24 hour periodicity
of the data. It is precisely this periodicity, however, that gives the
"prediction" technique employed here its accuracy. The variation of the
time delay is the highly correlatable quantity, and thus, the whole data
set - if available, should be used in the prediction scheme.
Monthly average regression lines were used in the analysis. The
slopes of the average monthly regression lines were within +20% from their
average for the whole period. The intercepts of the monthly lines of
regression were considerably more scattered.
For the two locales separated mainly in latitude (Fort Monmouth-
Richmond) the deviation of the "predicted" data from the observed data
was for the most part, within one standard deviation of the monthly data
set. For the daytime period, when the error introduced by the time-delay
is greatest, the ratio JDf/<T was even lower. When the average regression
line for the entire period considered was calculated (i.e., the average
of six monthly averages) , the bulk of the "predicted" data was still
within one standard deviation of the monthly data set. The ratio is
often high during time periods characterized by ionospheric disturbances.
For the two locales widely separated by latitude and longitude
(Richmond-Anchorage) , the deviation of the "predicted" data from the
observed data was, for the most part, within two standard deviations of the
monthly data set. When the average regression line for the entire
period was used, the bulk of the "predicted" data was still within the
two standard deviations of the monthly data set.
Since the monthly value of the standard deviation is r*25% of the
absolute value of the time delay, the method of prediction outlined here
appears to have the capability of correcting the time delay due to the
ionosphere to within "25% for stations separated in latitude, and />/50%
for stations widely separated in latitude and longitude.
D1 - 85
REFERENCES
Soicher, H. (1977): Ionospheric and plasmaspheric effects in satellite
navigation systems. IEEE Trans. Antennas & Propagation, Vol AP-25,
No. 5. "
Soicher, H. (1978a): Spatial correlation of transionospheric signal-
time-delay. IEEE Trans. Antennas & Propagation, Vol AP-26, No. 2.
Soicher, H. (1978b): Prediction of transionospheric signal time-delays
using correlative techniques. Proceedings of the Symposium of the
COSPAR Satellite Beacon Group on "Beacon Satellite Measurements of
Plasmaspheric and Ionospheric Properties", 22-25 May 1978,
Florence, Italy.
Soicher, H. (1979)* Correlation of satellite signal time-delays at
widely separated locations. IEEE Trans. Antennas & Propagation,
Vol AP-27, No. 6.
D1 - 06
2. HF IONOSPHERE-REFLECTED PROPAGATION PREDICTIONS
HF COMMUNICATIONS PREDICTIONS 1978
(AN ECONOMICAL UP-TO-DATE COMPUTER CODE, AMBCOM)
V.E. Hatfield
SRI International, 333 Ravenswood Avenue
Menlo Park, California 9^025 USA
An existing economical HF prediction code has been extended to incorpo-
rate the following features: sporadic E modes and losses on reflection and
transmission, a model of the auroral ionosphere, and a model of auroral
absorption that varies with magnetic activity. In addition to the homing
procedure that was available in the original program for point-to-point
communications, a surveillance capability (for OTH radar or other purposes)
has been included. New output options include contour maps of signal-to-noise
ratio plus raypath and wavefront plots.
1. INTRODUCTION
Recent program development at SRI International on the computer code
AMBCOM has incorporated the latest information on ionospheric features that
affect communications at HF into a predictions code that is both easy and
economical to use. It was also considered important to provide output that
would give useful information to communication planners and data analysts.
The computer code (called AMBCOM for ambient ionospheric communication pre-
dictions at HF) has been tested extensively in connection with a recent
contract for the U.S. Army Ballistic Missile Defense Advanced Technology
Center.
2. GENERAI DESCRIPTION OF THE CODE
The AMBCOM computer code uses as its basis the NUCOM code developed by
SRI during the 1960s under sponsorship of the Defense Nuclear Agency. NUCOM
predicts the performance of HF communication systems under normal and nuclear
conditions (Nielson, 1967). f AMBCOM employs the raytracing and communication
system concepts of NUCOM, but it is intended primarily for ambient iono-
spheric communication predictions. The ionosphere is modeled with three
parabolic layers. Ionospheric tilts and critical frequency gradients are
taken into account by specifying the parabolic parameters at as many as 41
points along the path. These parameters are derived initially from the
References are listed at the end of this paper.
D2 - 1
Institute For Telecommunication Science* (ITS) coefficients and are then
modified to incorporate the new features described in Sections 3, 4, and 5.
If desired, actual measurements may be used in place of the parameters. The
propagation analysis consists of a rapid, semianalytic, two-dimensional ray-
tracing routine based on the Kift-Fooks method. Both topside and bottomside
reflections from the normal ionospheric layers are allowed.
As originally developed, NUCOM computed propagation losses with a homing
feature for evaluation of specific point-to-point communication circuits;
binary error rates and signal-to-noise ratio were calculated. The new
program now also has the option of evaluating the area surveillance capa-
bility of over-the-horizon (OTH) radar; signal-to-noise ratio is calculated
and jammers may be introduced. Other features include homing from an ele-
vated moving target and plotting of ray paths and wave fronts.
Several improvements have been made in the ionospheric model and loss
mechanisms. These improvements include: a new model of the electron density
profile in the high- latitude ionosphere; a model for computing auroral
abosrption; and models for estimating reflection and obscuration losses for
the Es layer; both topside and bottomside reflections from the Es layer are
allowed. These improvements are especially useful for the evaluation of
elevated, or ducted, modes of propagation across the auroral zone.
A number of different mechanisms that can result in elevated modes are
simulated in AMBCOM. The chordal modes produced by ionospheric tilts, or
electron density gradients, and the ducted modes that are successively
reflected between the bottom of the F layer and the top of the normal E layer
were both incorporated in the original NUCOM code. The improved code
predicts, in addition, those ducted modes that are successively reflected
between the F layer and the Es layer.
In the next sections the new features are described in detail : The
high- latitude ionosphere model, the auroral absorption model, and the
sporadic E model. Finally, a few examples of the output capabilities are
shown.
3. HIGH- LATITUDE IONOSPHERE MODEL
The new code represents auroral oval phenomena as functions of Kp, cor-
rected geomagnetic latitude and time, and solar zenith angle. The oval
expands and moves south with increased Kp, and the midlatitude trough is a
feature on the nights ide.
The auroral morphology is implemented by incorporating two auroral
features that affec*- propagation significantly: A Kp-dependent F- layer
critical frequency and a Kp-dependent auroral E critical frequency. The
F- layer model is taken directly from the Rome Air Development Center (RADC)
polar model developed by Elkins and co-workers (1973). The auroral E-layer
Now called the National Oceanic and Atmospheric Administration
D2 - 2
model was developed from Chatanika, Alaska incoherent scatter radar measure-
ments of electron density profiles in the auroral ionosphere; this feature
was added by SRI to the RADC-POLAR model (Vondrak et al., 1978), under
contract to RADC. The auroral E is combined with the solar-controlled E to
define a single "equivalent" layer at the E- layer height.* This method seems
appropriate since the auroral E, unlike sporadic E, has a substantial semi-
thickness (Vondrak et al . , 1978).
No attempt was made to reproduce the unusual profile shapes found in the
auroral zone (Vondrak et al . , 1978) because of the requirement that profiles
must be represented by parabolas to permit use of the analytic raytracing
procedure. However, because the ionosphere generator for AMBCOM auto-
matically generates an F\ filler layer that is defined by E and F2 parameters
the resulting profiles are often reasonable approximations to auroral pro-
files. Modification of this filler algorithm to better represent a variety
of shapes, would be a welcome improvement in the code.
For demonstration purposes, a sample path over the pole was chosen.
Transmission from latitude 47 °N, longitude 69°W to 50°N, 90°E was simulated
using first the ITS ionosphere and then the AMBCOM auroral ionosphere with Kp
values of 2.6 and 5.0. The case run was September 1200 UT, and a sunspot
number of 100. Figure 1 shows the critical frequencies of the E- and F- layer
along the path for each of the 3 cases. Figure 2 compares the mode structure
for the ITS model with those modes that occur when the auroral model is used
(two values of Kp are shown). Modes are shown schematically and are termi-
nated after 5 hops; termination prior to 5 hops implies either penetration or
a distance limit. Introduction of the auroral model causes the following un-
conventional modes to occur: (1) Topside reflections occur for a Kp of 2.6
at 10 MHz for a take-off angle (A) of 25°, and at 12 MHz for A = 15 ; (2) A
perigee ray occurs for a Kp of 2.6 at 14 MHz with A = 15°. Figure 3 shows
ray paths generated by the program for the three cases at a frequency of
12 MHz and increments in elevation angle of 5°.
Unconventional modes are often initiated by negative ionization gradients
along the path; however, this occurs at a given frequency only over a limited
range of elevation angles. For example, an elevated mode appears in Figure 3
for A = 15° for the case of Kp = 2.6 (center of plot); the corresponding
gradient can be seen in Figure 1. It can also be seen from Figure 1 that the
gradient is larger for Kp = 5, but no elevated mode occurred for the five
take-off angles considered. A search on take-off angles would probably reveal
a similar elevated mode in this case.
4. THE AURORAL ABSORPTION MODEL
The auroral absorption model is a function of Kp, season, solar activity,
and corrected geomagnetic (CGM) latitude, longitude and time. It was devel-
oped from riometer measurements at approximately 30 MHz. Absorption values
The E- and F- layer heights in the RADC- Polar model are sometimes incon-
sistent with heights generated by the ITS coefficients; for simplicity, the
ITS heights were retained in the AMBCOM model.
D2 - 3
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AURORAL MODEL
Kp = 5.0
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25 NONE NONE NONE
NOTE: Calculations limited to five hops.
±
Penetrated . Distance cut off.
Perigee rays.
FIGURE 2 COMPARISON OF STYLIZED RAYPATHS AT VARIOUS TAKE-OFF ANGLES FOR
ITS MODEL, AND AURORAL MODEL Kp = 2.6, AND Kp = 5.0
D2 - 5
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given by the basic model of one-way- vertical absorption at 30 MHz are con-
verted appropriately for the angle of passage through the D-region and the
operating frequency.
The model in AMBCOM was developed on the RADC contract mentioned in
Section 3 (Vondrak et al., 1978) and uses a method proposed by Foppiano (1975)
as its basis (i.e., the formulation of the dependence on CGM coordinates,
season, and solar activity). The K~ dependence was derived from averaged
curves published by Hargreaves (1966). The final model was then calibrated
with riometer data from College, Alaska, which had been used in developing
the Basler (1963) model. Figures 4 and 5 show contours of one-way- vertical
absorption at 30 MHz over the auroral zone for Kp = 2.6 and 1, respectively.
The scale is CGM latitude versus CGM time; the longitude is constant. The
figures show the expected variation in absorption as a function of time of
day. Absorption effects of two kinds of particle precipitation (Hartz and
Brice, 1967) can be seen in Figure 4. Around midnight there is a slight peak
in absorption which is attributed to the "splash" type of precipitation; and,
in the morning hours, there is a larger peak attributed to "drizzle" pre-
cipitation. All parameters in Figure 5 are the same as in Figure 4, except
that Kp = 1.
5. SPORADIC E MODEL
Differences of opinion on how sporadic E (Es) should be handled in a
propagation prediction program have prompted us to provide several options.
The user may choose the one that is most suitable for his problem. The
options include rays that penetrate the Es layer as well as ones that reflect.
The specific options require that: (1) frequencies such that the equivalent
vertical frequencies are less than fQEs always reflect, (2) equivalent
vertical frequencies less than the blanketing frequency fDEs reflect, while
greater frequencies penetrate, (3) all frequencies penetrate, and (4) no
Es is to be considered. Both reflection and obscuration losses are included
in the first three options, with a choice of two methods of computing the
losses.
Values of fQEs are obtained from median, upper, and lower decile values
of the ITS coefficients. The median value of fQEs is normally used, but the
user may override this with any percentage he desires. We consider Es as
being present if fQEs is greater than f0E. This rule is based on the fact
that the method used in compiling statistics for the coefficients substituted
fQE when no Es was present.
The blanketing frequency, fj-,Es (in MHz) is calculated as a function of
latitude (lat) and night or day from the following equation:
f, E = L E H = (.5 + .2 (SSN/100)) f E |lat| ;> 70
b s b s v os
= f, E L = .65 f E night I lat I £ 50
b s os
= .9 f E day
os
D2 - 7
"fCrED OfOMAONf't '
FIGURE 4 CONTOURS OF MEDIAN ONE-WAY VERTICAL ABSORPTION IN dB AT
30 MHz ON A PLOT OF CORRECTED GEOMAGNETIC LATITUDE vs.
CORRECTED GEOMAGNETIC TIME, USING THE SRI ABSORPTION
o
MODEL. Corrected geomagnetic longitude, 260 ; sunspot number, 120;
month, 1 2; Kp = 2.6.
FIGURE 5 CONTOURS OF MEDIAN ONE-WAY VERTICAL ABSORPTION IN dB AT
30 MHz ON A CORRECTED GEOMAGNETIC LATITUDE-CORRECTED
GEOMAGNETIC TIME GRID, USING A LOW Kn (Kn = 1). Corrected
O fi -P
geomagnetic longitude, 260 ; sunspot number, 120; SRI absorption model.
D2 - 8
f,E - f E H(|lat|-50)/20 + f E L(70- | lat | )/20 50 < |lat| < 70
where the superscripts H and L refer to high and low latitude respectively.
These estimates of fbEs are based on the data presented by Kolawole (1978).
The Es model in AMBCOM is a thin layer (1 km semithickness) at a height
of 110 km. This height is slightly below the height of the normal E- layer
peak electron density (assumed to be 115 km in AMBCOM). This type of Eg is
typical of temperate and low latitudes (Leighton et al . , 1962). In this
current implementation of the Es option, upgoing rays that reflect from the
E layer ignore the normal E- layer ionization below 110 km, while rays that
penetrate are refracted in the normal E layer. Rays reflecting from the top-
side are first reflected from the normal E if possible. On penetration of
the normal E the rays may still be reflected from the Es layer. In this case
the reflection is performed without refraction in the E layer.
Two methods are available for the loss calculations. One model is based
on results published recently by Sinno and co-workers (1967); the other is
that published in the early 1960s by Phillips (1963). In the absence of more
extensive experiments measuring both reflection and obscuration loss, it is
difficult to determine which method is the more accurate. Figure 6 compares
the two methods for a sample case. The variable on the horizontal axis is
p = f cos i/f0Es; f is the operating frequency and i is the incidence angle.
Reflection normally occurs for p ^ 1. Curves are labeled with the ratio of
blanketing frequency fbEs/foEs.
6. EXAMPLES OF OUTPUT CAPABILITIES OF AMBCOM
For communication planning, the new option that provides contour maps of
signal-to-noise ratio (SNR) can be extremely useful. Contour maps of best
SNR by frequency, or best SNR for all frequencies, can be generated by the
program. Figure 7 shows contours of best SNR for all frequencies for an OHD
backscatter site located at 42° latitude, 100°W longitude with the antenna
pointing toward the west. Antenna patterns can be specified, but constant
gain was assumed in this case. The maps are produced from propagation pre-
dictions made along radials extending from the OHD backscatter site at
specified azimuthal directions. Figure 8 shows a sample of plots that can be
made along each radial. The envelope of the best signal is used in the con-
tour program (e.g., Figure 7). Azimuths are chosen at close enough increments
so that significant changes in the ionosphere will not be missed. A capa-
bility for including jammer effects is also available. For this option propa-
gation predictions are made at the azimuth of the jammer. The geographic out-
line map may be automatically generated to the specified scale for any desired
location.
The option of raypath plotting is also a new feature. "Homed" rays
between two sites or "ray sets" (shown in Figure 3) may be plotted. An option
of plotting wave fronts at specified time delays is also available.
D2 - 9
00
en
O
LU
<
z
o
in
w
o
z
o
I-
<
DC
D
O
w
CO
o
<
LU
z
o
10
20
30
40
PHILLIPS
SINNO
1.2
1.4
1.6
p = f cos i/f E
FIGURE 6 COMPARISON OF PHILLIPS AND SINNO Es LOSS METHODS FOR SEVERAL
BLANKETING FREQUENCY RATIOS (0.6, 0.7, 0.8, 0.9). Operating frequency
6 MHz; f0Es distribution; lower, median, and upper deciles = 3, 4, 7.
02-10
FIGURE 7 SIGNAL-TO-NOISE RATIOS FOR COMBINED FREQUENCIES (8, 12, 16 MHz)
January; 20 UT; 75 SSN; site at 42° N, 110° W.
D2 - 11
I
CM
LL
LU
M I]
o
to
o
8
§
3
O
oc
O
o
cm'
3
CO
LO
CO
CO
LU
Z
Z)
- >
o
LL
LU
o
z
<
I-
co
Q
Q
z
D
O
OC
a
o
i-
o
z
ID
co
<
O
<
or
LU
co
9P — HNS
a
CO
00
LU
OC
D
o
D2
12
7. COMPARISON OF AMBCOM PREDICTIONS WITH MEASUREMENTS
The ionosphere generator in AMBCOM consists of several parts, some of
which have previously been verified against substantial quantities of data.
For midlatitude paths the predictions remain the same except for optional Es .
Consequently, the comparisons presented in Nielson et al., 1967 remain
applicable. Good agreement was reported between observed and predicted
median MUFs and signal strengths for several midlatitude paths. Moreover,
oblique ionograms synthesized by raytracing showed remarkably good agreement
with observed mode structure. Similarly the models of the auroral F region
and the polar cap ionosphere are essentially those developed by RADC from a
large data base. The two sporadic E models were developed elsewhere and
verified as well as possible by their originators.
Only the models of the auroral E- layer and the Kp- dependent auroral
absorption are new. The former was developed by SRI from a limited set of
data during low solar activity (all of the 24-hour Chatanika data available
at the time). The absorption model was based on riometer data also from a
limited set. Clearly further research is needed to verify and extend these
models to a wider range of conditions.
As important as independent verification of all of the models themselves
is verification of HF signal strength measurements on several long trans-
auroral paths and on several paths where Es effects may be assessed.
8. CONCLUDING REMARKS
Most of the available raytracing programs are either very time-consuming,
as in numerical integration procedures, or too simplified to permit the
introduction of large gradients such as those that occur in auroral and equa-
torial regions. The value of the AMBCOM program lies in its ability to
incorporate tilts and topside reflections while still remaining economically
attractive.
A comparison of running times and storage requirements for four specific
programs used at SRI International is shown in Table I. The reader is
cautioned that many variables affect the comparisons and the numbers shown
are estimates based on a number of specific cases. The cost is normalized
to that of AMBCOM.
D2 " 13
Table I
Comparative Running Times and Storage Requirements Estimated
From a Limited Set of Computer Runs on a CDC 6400 Computer
Program
Normalized Cost
(Running Time)
Maximum
Central Memory Required
Description
RADARC
.6
AMBCOM 1 . 0
CRT 1.43 10.0
AFCRL 3-D 100.0
140000
8
146000
8
137000
8
106700
8
SRIs Version of HMUFES
(Barghausen 1969)
A 2-D incremental
raytrace
A 3-D incremental
raytrace. March 1975
version
9 . ADDENDUM
Recently (after the present paper had been submitted) a brief study was
undertaken internally by SRI to further verify the RADC model, particularly
within the polar cap. Predicted E and F-region critical frequencies were
compared with VI ionosonde data from Fort Churchill (an auroral station) and
Resolute Bay (a polar cap station). Good agreement was found for Fort
Churchill and for fGF2 at Resolute Bay. However, significant differences
were noted for f0E inside the polar cap. On the basis of these results a
modification was made in AMBCOM that results in significant changes within
the polar cap. (These changes have not been made in Figures 1 and 2 of this
paper. )
D2 - H
REFERENCES
Barghausen, A. L. , J. W. Finney, L. L. Proctor, L. D. Schults (1969):
Predicting long-term operational parameters of high-frequency sky-wave
telecommunication systems. ERL 110- ITS, ESSA, Department of Commerce,
Boulder, Colorado.
Basler, R. (1963): Radio wave absorption in the auroral ionosphere.
J. Geophys. Res., 68:4665.
Elkins, T. and C. Rush (1973): A statistical predictive model of the polar
ionosphere. In an Empirical Model of the Polar Ionosphere, AFCRL-TR-73-
0331, Air Force Cambridge Research Laboratories, L. G. Hanscom Field,
Bedford, MA.
Foppiano, A. (1975): A new method for predicting the auroral absorption of
HF sky waves. CCIR, IWP 6/1, Docs. 3 and 10.
Hargreaves, J. (1966): On the variation of auroral absorption with
geomagnetic activity. Planet. Space Sci., 14:991.
Hartz, T. R. and N. M. Brice (1967): The general pattern of auroral particle
precipitation. Planet. Space Sci., 15:301.
Kolawole, L. B. (1978): The transparency characteristics of Es types.
Radio Sci., 13:159.
Leighton, H. I., A. H. Shapley, and E. K. Smith (1962): The occurrence of
sporadic E during the IGY. In Ionospheric Sporadic E, Pergamon Press,
London, 166-177.
Nielson, D. L. , J. B. Lomax, and H. A. Turner (1967): The prediction of
nuclear effects on HF communications. DASA 2035, Final Report, Contract
No. DA-49-XZ-436, Stanford Research Institute, Menlo Park, CA.
Phillips, M. L. (1963): Auxiliary procedures used in theoretical evaluation
of HF backscatter observations and other communications problems.
External Technical Memorandum No. E14, ITT Electro- Physics Laboratories.
Sinno, K., M. Kan, and Y. Kirukawa (1976): On the reflection and transmission
losses for ionospheric radio wave propagation via sporadic E. J. Rad.
Res. Labs, Japan, 23:65.
Vondrak, R. R., G. Smith, V. E. Hatfield, R. T. Tsunoda, V. R. Frank, and
P. D. Perreault (1977): Chatanika model of the high-latitude ionosphere
for application to HF propagation prediction. Final Report, Contract
F19628-77-C-0102, SRI International, Menlo Park, CA.
D2 - 15
THE STATISTICAL PROPERTIES OF THE DISTURBED HIGH-LATITUDE
IONOSPHERE IN RADIO WAVE PROPAGATION COMPUTATIONS
E. M. Kovalevskaya and E. M. Zhulina
Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation
of the Academy of Sciences of the USSR
Moscow Region, USSR
A practical method for taking into account statistical proper-
ties of the disturbed high latitude ionosphere in radio wave propa-
gation computations is described. Material is presented as easily
readable plots for various ionospheric conditions. This manual
makes it possible to determine, apart from the reliable estimates
of the boundaries of the examined characteristics, the range of
their variations for a month and the variations due to disturbances
Calculations show that in high latitudes the confidence limit of
one hop distance can be extended up to 1,000 km, while in middle
latitudes these limits do not exceed 200-300 km. The confidence
limits of azimuthal deviation may reach 1°.
Practical radio communication and studies of the problems of radio wave
propagation often give rise to a need to know the confidence limits of varia-
tions in one or another characteristic. Existing practical instructions have
usually been calculated for average conditions, and therefore additional cal-
culations are required to find the intervals of variations in these character-
istics. The present manual gives information relevant to variations of the
hop distance and azimuthal deviations due to the statistical variations in
the ionosphere. The material is set out in easily readable plots for the
various ionospheric conditions (Figs. ]-k) . It is possible to determine,
apart from the reliable estimates of the examined characteristics, the range
of their variations for a month and the variations due to disturbances. The
manual can be used to calculate the radio links through high latitudes since
the inhomogenei ty and increased disturbance of the ionosphere in such region's
result in a broad range of variations of the characteristics. The following
input data should be set when using the manual: the height, hmF2, and half-
width, ymF2, of the maximum of F2; the value of error, y, or deviation of
foF2 from the median due to disturbance; the values of the elevation angle A;
and the operating-to-critical frequency ratio, f/fo.
The main concepts taken into account when writing the manual are con-
sidered below.
It has been shown by studying the statistical variability (SV) of the
ionosphere (Zhulina and Kiseleva, 197*0, using foF2 as an example, that in
D2 - 16
013 km
10001
hm =-500hm
ijm = WO KM
0 2 4 6 8 10 12 H 16 16 20 22 24 26 2& 30 A*
Fij.1
JknmM
hm = 300 KM
%-i00KM
0 2 4 6 6 10 12 3 16 Ti 2022 2*26 2830 A
JU/oF2=20%
tin ^300 KM
U^ = 100 KM
t i i i i r 1— i 1 1 i i i t i
0 2 4 6 8 10 12 ft 16 16 202224 262650 A"
Fij.2
hm=300KM , ym= 100km, df0/ty=03l0 MHjm
Wo'2.0
F^.3
0 0J 1 15 2 25 0 0J 1 15 2 2.5 10 A
D2 - 17 Fij-4
the middle and low latitudes, the normal law of distribution may be used in
many cases to describe SV. The normal law of distribution is indicative of
the random nature of the distribution of sampled values and their indepen-
dence. In this case the median foF2 and the mean over the set, which form
the basis of the calculations of all the characteristics of radio wave propa-
gation, are representative estimates and can characterize, with sufficient
reliability, a mean monthly state of the ionosphere. Although their determin-
ation as statistical values contains some error y (which we shall call the
natural error), if the normal law is satisfied, the error y is of random
nature.
The foF2 distribution in high latitudes is more complex (Zhulina and
Kiseleva, 197^). Apart from the random component, the distribution comprises,
as a rule, a systematic component, which is due to the dependence of the
values on common nature. The latter is the source of the disturbance, namely
the corpuscular penetrations resulting in ionospheric disturbances which last
for many hours or even days. In middle latitudes, this component is of small
value in most cases, whereas in high latitudes it is dominant. This circum-
stance affects the accuracy of the calculated value X = x ± ty , where t is
the parameter in the student distribution determining the confidence limits
(ty) . In the general form, the error is the sum of two terms, namely, the
independent (the first addend) and the dependent components:
v - Ao2[l + (n - 1)t]
n
where n is the number in the sample, Oq2 is the variance, and t is the auto-
correlation coefficient.
Calculations have shown that in the middle latitudes, and in the case of
a normal distribution in high latitudes, the error y is small (2-5 percent)
and, correspondingly, the limiting error (for a_0.95 probability) is below
12 percent. In this case, the error in foF2 = x is usually much below the
extrapolation error and the error due to the prediction of solar activity and,
therefore, is usually neglected in practical calculations.
In high latitudes, the reliability in determining x is much lower. In some
cases, the errors may reach kO percent. Some results of the calculations of
the natural errors are presented in Table 1. Included are the values of
oq = (foF2 - foF2;/foF2) , x, the coefficients of asymmetry and excess, and the
character of the distribution for some stations located in various latitudes.
It can be seen from the table that the errors in foF2 due to disturbances in-
crease up to 20-40 percent (with the maximum in the center of the auroral
zone) at high latitudes in winter and in equinox, excluding the evening
hours. The significance of the variations in the propagation characteristics
resulting from the foF2 natural errors can be determined. Further consider-
ation was given to the variability (a) of the hop distance dD for reflections
from the F2 region, disregarding the horizontal i nhomogenei ty in the plane of
the great circle path, and (b) of the deviations of angles in the horizontal
plane due to the horizontal i nhomogene i ty of the electron concentration of
the F2 region. The calculations have been made for a one-layer parabolic
ionosphere on the basis of the program published in Kerblay and Kovalevskaya
(197M- The value of dD was determined as the difference in the hop distance
in the presence and absence of the foF2 error:
dD = DfoF2 - DfoF2(y)
D2 - 18
Table 1. Values of parameters at various stations
Stat ion
Period
of
Year
°o
A
E
T
tu
Distri-
Observation
bution
Ki runa
summer
day
1967
11.2
0.33
0.53
0.15
8.6
N
Murmansk
summer
morning
1964
12.8
0.53
0.3
0.03
4.4
N
Salekhard
summer
day
1969
13.2
0.86
-2.63
0.06
6.8
N
Sverdlovsk
summer
day
1964
8.2
-0.11
1.85
0.1
5.4
N
Murmansk
equin.
day
1968
15.6
-3.36
-3.19
0.14
11.4
N
Murmansk
equin.
night
1968
19.6
-0.16
0.6
0.41
25.0
B
Murmansk
equin.
day
1964
18.4
0.2
0.13
0.15
14.2
N
Dixon
equin.
day
1968
27.3
-1.13
3.03
0.27
18.0
AE
Salekhard
equin.
night
1968
23.8
0.06
-0.53
0.56
35.6
AE
Salekhard
equin.
night
1964
22.8
0.32
-0.32
0.46
28.0
AE
Leningrad
equin.
night
1968
23.7
0.17
-0.4
0.04
10.8
N
Resolute Bay
equin.
night
1958
20.2
0.21
2.58
0.2
18.2
N
Murmansk
wi nter
morning
1968
33.8
-7.96
-8.46
0.46
46.0
B
Murmansk
wi nter
night
1971
23.6
-0.26
-0.6
0.53
34.8
B
Dixon
winter
day
1968
25.9
-0.43
-0.43
0.46
35.4
B
Dixon
wi nter
morning
1964
21.9
12.7
I4ii
0.54
32.2
B
Salekhard
winter
night
1971
32.2
0.2
-1.1
0.43
42.3
B
Salekhard
wi nter
day
1964
24.8
-6.8
-7.2
0.42
32.0
E
Leningrad
winter
night
1971
19.2
0.21
-0.43
0.2
17.4
N
Leningrad
winter
day
1971
12.4
1.01
4.11
0.2
11 .2
N
1N = normal ;
B = bi modal ; A =
asymmetric;
E = excessive
distr
ibut ions
The results of separate calculations of dD for the errors y , which are
5, 20, 30 percent, are shown in Figures 1-3. The solid and dashed curves in
the plots correspond to the negative and positive deviations of foF2, re-
spectively. The numerals on the curves show the ratio of the operating fre-
quency to foF2 (f/foF2) . Also marked on the curves are the transitions of
the low ray to the Pedersen ray. Figure 4 presents the plots of the lateral
deviations da for the errors y equalling 0, 10, 20, 30, and 40 percent.
The plots presented in Figures 1-4 may be used also to estimate the dD
and da variations during negative or positive disturbances. In this case,
the value of y will denote the foF2 deviation due to disturbance. The nega-
tive and positive disturbances will result in an increase and decrease of the
hop distance, respectively. It can be seen from Figures 1-3 that when the
error in foF2 equals 30 percent, and propagation is by the usual ray, the
value of dD usually fails to exceed 200 km even for the longest links. This
value corresponds approximately to the accuracy of the calculations. The
values of dD do not exceed 200 km even at y = 10 percent in most cases up to
f/foF2 = 2.6. At y = 20 percent and higher, however, the value of dD can no
longer be neglected. For example, in the links traversing the zones where y
is 30-50 percent, the dD variations may be 400-800 km. With regard to the
Pedersen ray, when y = 10 percent, the dD variations are larger than 200 km.
A relevant specific example is as follows. Given the ionospheric parameters
hm = 300 km, ym = 100 km, A = 4°, f/foF2 = 2.0 in middle latitudes, when the
error y is small, the hop distance will be 2600 km. In high latitudes, due
to the 30 percent statistical error, the hop distance will be 2600 + 340 km.
D2 - 19
When the ratio f/foF2 = 2.2, the correction for one hop will be as much as
620 km.
The following example shows the degree of variation in the angle a of the
azimuthal deviation as a function of the statistical error of the distance.
For the initial conditions f/fo = 1.8, D = 1800 km, the value of a at y = 0%
will be about 0.1°. At y = -20% or on the days with negative disturbances, a
will increase up to - 0.3° and, in the case of the Pedersen ray, up to 1.8°.
At positive y or for positive disturbances resulting in an increase of foF2,
a wi 1 1 decrease. The example presented above shows that the effect of the
statistical error may be comparable with, and in some cases exceed, the calcu-
lated value of a proper.
Indicated above were only the errors in determining the median values of
the hop distance and the angles of azimuthal deviations relevant to the sta-
tistical properties of the medium. The statistical variability of one or
another parameter X as a whole (variations from day to day) must be described
using the formula
X = x ± UOq
where u is the parameter of the normal distribution (u = 2 for P = 0.95).
In middle latitudes, the statistical scatter characterized by the term
uoq is, as a rule, significantly in excess of the confidence limit of the
median estimates. In Leningrad, for example, in the equinox of 1968 at night,
ty = 10.8% and ua0 = 2 x 23-7 = **7%. In the disturbed medium (for example,
in the high latitudes), the values of ty and ucjq become comparable (see the
same case for Murmansk, ty = 25%, uoq = 2 x 19-6 = 39%), which is indicative
of low reliability in the median values. The calculations presented above
show that in high latitudes, where errors in the median ionospheric parameters
increase significantly due to their statistical nature, the main character-
istics of propagation as well as the reliable limits should be calculated
thereby permitting a higher accuracy of prediction of one or another feature
of radio wave propagation.
REFERENCES
Kerblay, T. S., and E. M. Kovalevskaya (197^): Trajectories of Short Radio
Waves in the Ionosphere. Nauka, Moscow.
Zhulina, E. M. , and M. V. Kiseleva (197^): About features of statistical
distributions of 6foF2 in high latitudes. In: Study of the F-Region
and Outer Ionosphere, IZMIRAN, Moscow, 275.
D2 - 20
PREDICTION OF HF COMMUNICATION DISTURBANCES BY PRE-SC
HF FIELD INCREASES ON POLAR PATHS CROSSING THE AURORAL ZONE
T. ONDOH and K. OBU
Radio Research Laboratories, Tokyo, 184, JAPAN
Analysis of WWV field variations of the polar path received
at Hiraiso, Japan shows that WWV field increases of about 10 -
20 dB are often observed at frequencies above 20 MHz for about
10 hours before geomagnetic storm sudden commencements. The
pre-sc WWV field increases are accompanied with ionospheric fQF2
increases over approximate apexes around the noon on the polar
paths. The pre-sc WWV field increases may be due to decreases
of the ionospheric deviative absorption for HF waves associated
with polar cusp fQF2 increases, which are caused by precipitations
of enhanced polar cusp electrons with energy of 1 - 2 keV.
Consequently, the pre-sc HF field increases on polar paths crossing
the auroral zone are useful for the prediction of HF communication
disturbances associated with geomagnetic storms in the solar quiet
period.
1. Introduction
Since geomagnetic storms in the solar quiet period have no definite causal
phenomena on the solar disc, a study on precursors of geomagnetic storms is
important for the radio warning service, especially in the solar quiet peri-
od. At the Hiraiso Radio Warning Center, Japan, it has been experimental-
ly known since the IGY that increases in the field intensity or receiving
time of WWV 20 MHz propagating from Washington D. C. , U. S. A. often occur
before geomagnetic storms. The Washington-Hiraiso path traverses the
northern auroral zone, and also the polar cusp region in geomagnetically
disturbed periods. So, it is expected that particle precipitations through
the polar cusp give some effect upon HF propagation on the Washington-Hiraiso
paths. In this paper, we first analyse statistically storm-time variations
of WWV 20 MHz field intensity received at Hiraiso, Japan and of fQF2 at ap-
proximate apexes of the Washington-Hiraiso path in order to elucidate the
pre-sc field increases of WWV 20 MHz at Hiraiso. Secondly, we also derive
statistically the storm-time variations of WWV field intensity on 25 MHz, 20
MHz, 15 MHz, and 10 MHz, and of f0F2 observed at Canadian ionospheric sta-
tions for the above purpose. Finally, applied results of the pre-sc field
increase of WWV 20 MHz to the radio warning service at Hiraiso are reported
in the solar quiet period for 1962 - 1965. All WWV field data used in this
paper are of radio waves propagating from the transmitting station at Wash-
ington, D. C, although the WWV transmitting station was later transferred
from Washington, D. C. to Fort Colins.
D2 - 21
2. Ionospheric Stations Used and Method of Data Analysis
Ionospheric f0F2 an<^ WWV field intensity data used in this paper were ob-
served at ionospheric stations in Canada, Alaska, and Japan for 1957 - 1959.
Table 1 gives geomagnetic co-ordinates of the stations used. We select 50
geomagnetic storms occurring during August, 1957 to February, 1959.
Table 1. Ionospheric stations used
Station
Geomag. Lat.
Geomag. Long.
Thule
88.0°N
1.1°
Eureka
86.5°N
236.4°
Alert
85.8°N
168.5°
Resolute Bay
82.9°N
289.3°
Baker Lake
73.7°N
315.1°
Ft. Churchill
68.7°N
322.7°
College
64.7°N
256.5°
Fairbanks
64.6°N
256.6°
Meanook
61.8°N
301.0°
Winnipeg
58.8°N
322.9°
Ottawa
56.9°N
351.3°
Washington
50.0°N
350.3°
Hiraiso
26.2°N
206.3°
Since WWV field intensities at Hiraiso include ZAN, we obtain the storm-time
variation (Dst) of the medians of WWV 20 MHz field intensities observed at
Hiraiso for the 50 geomagnetic storms. The storm- time Tst is reckoned
from the occurrence time of geomagnetic storm sudden commencement (sc) , and
the storm-time variation (Dst) is derived by the superposed method at each
storm-time from Tst= -24 hours to 31 hours. Storm-time variations of fQF2
and WWV field intensity at Canadian ionospheric stations are obtained by
computing the average deviation of fQF2 or WWV field intensities from the
monthly median over the 50 geomagnetic storms selected. The disturbance, D
is expressed by D = Dst + Ds . The disturbance daily variation, SD is
obtained by the superposed method of DS at each local time. We also com-
pute the disturbance daily variation of f^o in the pre-sc stage for the 50
geomagnetic storms, in order to investigate an effect of the magnetospheric
process on the pre-sc WWV field intensity in high latitudes.
3. Pre-sc WWV 20 MHz Field Increases Received at Hiraiso
Fig. 1 shows a typical example of WWV 20 MHz field increase and an extens-
ion of WWV 20 MHz receiving hours at Hiraiso before an sc of 0323 UT on July
27, 1958. Since no significant geomagnetic disturbance occurred before
July 26, 1958, the record of WWV 20 MHz field intensity on July 26 represents
the quiet-day propagation condition. The receiving hours of WWV 20 MHz
before the sc of July 27 is about 4 hours longer than that on the quiet day
(July 26). So, it seems that WWV 20 MHz waves propagate from Washington,
D.C. to Hiraiso along the great circle path before the sc.
D2 - 22
—f-^jm -4 1 1! j -■•;"" :-
Fig. 1 Records of WWV 20 MHz field intensity received at Hiraiso showing
field intensity increases before an sc of 0323 UT on July 27,1958.
Fig. 2 shows storm-time variations of the median of WWV 20 MHz field in-
tensities received at Hiraiso over 50 geomagnetic storms which occurred with-
out polar cap absorption during August, 1957 to February, 1959. An upper
curve in Fig. 2 is the average storm-time variation of K- indices over the 50
geomagnetic storms at College, Alaska near an apex of the Washington-Hiraiso
path. A pre-sc WWV 20 MHz field increase of about 10 - 20 dB above the
quiet level is clearly seen from Tgt= -12 hours to the sc. It is expected
that an fQF2 increase at apexes of the propagation path causes an intensity
increase of HF waves at frequencies near the F-layer penetration frequency.
So, we derive storm-time average variations of fDF2 deviations from the
monthly median over the 50 geomagnetic storms at Fairbanks, Meanook, and
Winnipeg, where are near apexes of the Washington-Hiraiso path, in Figs. 3a,
3b, and 3c respectively. Figs. 3a - 3c clearly illustrate the pre-sc fQF2
increases at the above stations for Tgt= -20 hours - Tst= -2 hours which are
approximately the same storm-time interval as the pre-sc WWV 20 MHz field
Dsl ot K index oi College
■20
I UN
Dst of Median of WWV 20Mc/5 Field Intensify at Hiraiso
26 Tst
Fig. 2 Storm-time variations of K- indices at College, Alaska and of the
median of WWV 20 MHz field intensities at Hiraiso, Japan over the
50 geomagnetic storms during August, 1957 to February, 1959.
D2 - 23
Dst of A'oFj ol Fcirbonks
3b
3c
Dst of Af.Fi ol Meonook
Dst ol At.Ft at Winnipeg
Fig. 3 Storm-time variations of fQF2 deviations from the monthly median
over the 50 geomagnetic storms at Fairbanks (3a) , Meanook (3b) ,
and Winnipeg (3c) .
increase received at Hiraiso. Thus, it becomes clear that the pre-sc WWV
20 MHz field increase is closely related to the pre-sc fQF2 increase at the
apexes of the Washington-Hiraiso path.
4. Frequency Band of The Pre-sc WWV Field Increase in High Latitudes
For the purpose of finding preferential frequency band of the pre-sc WWV
field increase, we further analyse storm-time average variations of WWV field
D2 - 24
intensity deviations from the monthly median at 25, 20, 15, 10, 5, and 2.5
MHz over the 50 geomagnetic storms, using WWV data received at Ft. Churchill
and Winnipeg during August, 1957 to February, 1959. Figs. 4a and 4b show
storm-time average variations of WWV field intensity deviations from the
monthly median scaled in the S-unit at Ft. Churchill and Winnipeg respective-
ly. Pre-sc WWV field increases are clearly seen on 20 MHz and 25 MHz from
Tst= -20 hours to -4 hours at Ft. Churchill, while there is no pre-sc field
increase at frequencies below 15 MHz. However, any evident increase above
AS > 1 does not occur in the pre-sc stage on all WWV frequencies at Winni-
peg, where is located at geomagnetic latitude below the auroral zone.
Also, there is no systematic storm-time variation of 2.5 MHz field intensity
at Ft. Churchill. Thus, the pre-sc WWV field increase occurs on frequency
of 20 MHz and 25 MHz only at stations which have the WWV propagation path
crossing the auroral zone.
Storm-time average variations of fQF2 deviations from the monthly median
at Thule, Eureka, Alert, Resolute Bay, Baker Lake, Ft. Churchill, Ottawa, and
Washington D. C. are shown in Fig. 5 for the same 50 geomagnetic storms
during August, 1957 to February, 1959. The storm-time variations in Figs. 3a
-3c and 5 indicate that the pre-sc fQF2 increase occurs only at geomagnetic
latitudes between about 83°N (Resolute Bay) and 57°N (Ottawa). But, even
the storm time decrease of f0F2 does not occur at high latitudes above 85°N
(Alert). The pre-sc fQF2 increase at Winnipeg, where is the approximate
apex of the Washington-Churchill path, corresponds to the pre-sc WWV 20 MHz
and 25 MHz field increases at Ft. Churchill.
4.-i
Dsl ol AWWV 25 8 20 Mc/s at Ft. Church.il
25 Mc/s
20 Mc/s
D2 - 25
Dst of AWWV 50 8 25 Mc/s ol Ft Churchill
Oil of AWWV 25 a 20 Mc s of Winnipeg
25 Mc/s
20 Mc/s
Fig. 4 Storm-time variations of WWV field deviations from the monthly
median on 25, 20, 15, 10, 5, and 2.5 MHz at Ft. Churchill (4a)
and Winnipeg (4b) over the 50 geomagnetic storms.
5. Effect of Dayside Polar-cusp Electrons on the Polar Ionosphere
and Pre-sc HF Field Increases of Polar Paths
Disturbance daily variations (SD) of fQF2 in the pre-sc stage are obtained
in Figs. 6a - 6f by superposing fQF2 deviations from the monthly median at
each local time, using fQF2 observed at Resolute Bay, Baker Lake, Churchill,
Fairbanks, Meanook, and Winnipeg during the 50 geomagnetic storms respective-
ly. Figs. 6b - 6f show evident increases of the pre-sc SD component of
D2 - 26
Dsl of Af.Ft ol Resolute Boy
Fig. 5 Storm-time variations of fQF2 deviations from the monthly median
over the 50 geomagnetic storms at Thule, Eureka, Alert, Resolute
Bay,
Baker Lake, Ft. Churchill.
D2 - 27
fif.Fi
mca 6a
Q8
Ofa
SO of Pre-SC AfnFz ot Resolute Bay
04-
0?
00
-J 1 1 1 1 1 1 I 1_
0 4 8
Mc/k
20
LT
6c
Mc/s
I Oh
06
06
Q4
02
-02h
SD of Pre-SC AfoF» of Churchill
■ i i i i 1 iii'
20
LT
Fig. 6a - 6c Disturbance daily variations of f0F2 deviations from the
monthly median in the pre-sc stage over the 50 geomagnetic
storms at Resolute Bay (6a), Baker Lake (6b), Ft. Churchill
(6c), and Fairbanks (6d) .
fQF2 around the local noon in the auroral zone and higher latitudes below
82°N. The Ariel-A observation indicates that polar-cusp electron ( 1 keV
4 keV) intensities increase by a factor of 10 at 2 keV for magnetic local
D2 - 28
6d
SO of FVa-SC AfoFj at Fairbanks
Mc/s
OG
04
02
QO
I ■ i_
_l l_ 1 L_
20
LT
6e
Mc/s
Q8
06-
04
02
00
-Q2
_j i i_
SO of I'm SC Afo(? (il Meonook
-i ■ ■ ■ *
Af.Fi
Mc/s
Q4
02
00
-Q2
6f
SD of Pre-SC AfoFz at Winnipeg
20
LT
-i i i | '
20
LT
Fig. 6d - 6f Disturbance daily variations of f0F2 deviations from the
monthly median in the pre-sc stage over the 50 geomagnetic
storms at Meanook (6e) and Fairbanks (6f ) .
time of 11 - 13 hours during a period of northwardly directed interplanetary
magnetic field (Craven and Frank, 1978). A flux of 1 - 2 keV electrons,
10 cm .sec J-.eV l.ster 1 is required to account for the polar F-region a
at
D2 - 29
the winter solstice by the particle impact ionization (Kamiyama, 1966).
Therefore, the pre-sc increase of f0F2 around the local noon in high lati-
tudes can be explained by the impact ionization of low energy (1-2 keV)
polar-cusp electrons. Table 2 lists ranges of the pre-sc increase of fo^2'
The pre-sc increase of f0F2 in Table 2 may cause a deviative-absorption
decrease of the order of 10 - 20 dB for 20 - 25 MHz on polar paths. This
produces the pre-sc HF field increase at 20 - 25 MHz and the prolonged re-
ceiving hours of WWV 20 and 25 MHz on polar paths.
Table 2. Ranges of the pre-sc f0F2 increases
observed in high latitudes during
August, 1957 to February, 1959.
Stations
Af0F2
Resolute Bay
< 5.5 MHz
Baker Lake
< 5.5 MHz
Ft. Churchill
< 5.0 MHz
Fairbanks
£ 4.5 MHz
Winnipeg
< 4.0 MHz
6. Application of The Pre-sc HF Field Increase to The Prediction
of HF Communication Disturbance in The Solar Quiet Period
One of the most reliable means for the HF communication disturbance in the
solar quiet period is the 27-day recurrent geomagnetic disturbance. But,
there are a few recurrent geomagnetic disturbances continuing more than three
solar cycles. In this respect, the pre-sc HF field increases of polar
paths are useful means for the prediction of HF communication disturbances in
the solar quiet period. The HF communication disturbance associated with
geomagnetic storm on March 4, 1964 was first warned by this method at the
Hiraiso Radio Warning Center, though this storm was not predicted by the 27-
day recurrent geomagnetic disturbances. Since then, the pre-sc WWV 20 MHz
field increases have been successfully applied to the prediction of HF commu-
nication disturbances at Hiraiso Radio Warning Center.
Of 88 geomagnetic storms during January, 1962 to October, 1965, 56 pre-sc (or
sg) WWV 20 MHz field increases ( 64 %) were observed at Hiraiso, Japan.
The occurrence rate of the pre-sc (or sg) WWV 20 MHz increases at Hiraiso in
1962, 1963, 1964, and 1965 is 64 %, 68 %, 57 %, and 66 % respectively.
Thus, the pre-sc HF field increase on polar paths traversing the auroral zone
is a useful means for the prediction of HF communication disturbances,
especially in the solar quiet period.
References
Craven J. D. and L. A. Frank (1978) : Energization of polar cusp
electrons at the noon meridian. J. Geophysical Research, 83 : 2127.
Kamiyama H. (1966) : Ionization and excitation by precipitating
electrons. Report of Ionosphere and Space Research in Japan, 20:171.
D2 - 30
MINICOMPUTER SIMULATION OF IONOSPHERIC RADIOWAVE
PROPAGATION AT DECAMETRIC WAVELENGTHS
David D. Meisel
Department of Physics and Astronomy
State University College
Geneseo, New York ]kk5k, U.S.A.
Basil Duke
Transmission Systems
Canadian Broadcasting Corporation
Engineering Headquarters
Montreal, Quebec, Canada
Wi 1 1 iam D. Savedof f
Harvard University
Cambridge, Massachusetts 02138, U.S.A.
Initial experiments into the utilization of limited storage
minicomputers for simulation of ionospheric propagation conditions
on a worldwide basis are described with emphasis on prediction of
received signal strength as a function of local time, calendar
date, solar flux, and geomagnetic index. Comparison of the pre-
dictions with field strength measurements are made for several
long-distance paths.
INTRODUCTION
As a part of a previous study of HF, VLF, and geomagnetic behavior during
solar eclipses (Meisel, et al . 1976) a minicomputer program for simulation of
obi ique- incidence radiowave propagation behavior on one-hop and two-hop paths
was developed. Based on this experience, it was decided to extend this prog-
ram to long distance paths in order to see if solar eclipse effects could be
detected from remote receiving stations. In particular it was of interest to
see if the methods adopted by Haydon and others at the Institute for Telecom-
munication Sciences (ITS) [formerly the Central Radio Propagation Laboratory
(CRPL)] (CRPL, 1 9^*8; Ostrow, 1962; Davies, 1965; Leftin, 1975; Roberts and
Rosich, 1975; and Haydon, Leftin, and Rosich, 1976) could be modified to in-
clude the lower ionosphere details needed to simulate the observed solar ec-
lipse changes while at the same time fit the whole program into the memory of
a very modest sized electronic computer. Aside from the purely scientific ap-
plications of such a prediction program, there are some "commercial" possibi-
lities which could materialize once quantitative reliability has been estab-
1 i shed.
D2 - 31
The increased availability of electronic computers of moderate storage
capabilities (minicomputers) has been one of the most dramatic developments
of the last decade. Within the last year or so, ready-to-run "personal"
minicomputers have become available at prices comparable to home video recor-
ders. Thus, minicomputer simulation programs based upon those originally de-
veloped primarily for engineering studies of shortwave radio propagation
would probably be useful in a wide variety of situations including use by
governments of some third world countries, small broadcasting organizations
and telecommunication companies and perhaps also by advanced radio amateurs,
shortwave listeners, and radio engineering students.
COMPUTER REQUIREMENTS
In 197**, we started work on minicomputer ionospheric programs with a
slightly modified 8K FOCAL compiler package using a standard 8K (12 bit words)
memory Digital Equipment Corporation PDP-8/L computer belonging to the State
University of New York-Geneseo (Physics and Astronomy Department) at Geneseo,
New York. Two FOCAL programs are now available with corresponding BASIC ver-
sions in production. The first FOCAL program calculates the field strengths
incident on the receiver location. The second FOCAL program inputs and uses
incident field strength data generated by the first program to calculate the
receiver input voltage. In FOCAL, both programs just fit into 8K memory com-
puters. In BASIC somewhat larger memories appear to be required but the 16
bit words enable higher accuracy to be obtained. Adaptation of the FOCAL ver-
sions to minicomputers without FOCAL compilers also appears to be feasible,
but no attempt has been made to actually do this yet. Although the minicom-
puter programs described here were developed independently of the latest NBS
work, the input-output formats and purposes are remarkably similar.
In this paper, we describe only the ionospheric calculation part of the
program set. The receiving antenna program has not been finalized so it will
be described at a later date.
THE CALCULATIONS
As a starting point, we began with the CRPL methods described by Haydon
in NBS Monograph 80 (Davies, 1965). Gradually the FOCAL program has evolved
from strict application of the CRPL- 1 966 methods to unique algorithms which
include semi -empi r ical corrections for a variety of effects not originally in
the CRPL treatment but as a check on the calculation the CRPL- 1 966 path loss
formula was originally used parallel to our own method. Since the program
length must be kept within modest bounds, many approximations and lineariza-
tions have been made. Items included, at least to a first approximation, are:
(a) F2 critical frequencies - first order
(b) magnetionic effects - full polarization treatment
(c) ground reflections - full polarization treatment for land or sea
(upon option)
(d) E, Fl , and Es cut-off effects - the Es is optional
(e) deviative absorption - assuming parabolic layers
D2 " 32
(f) F2 virtual height variations - calculated for path mid-point
(g) auroral absorption - includes general polar as well as "ring"
(h) magnetic storm effects - includes depression of F2 frequencies
(i) signal fading and polarization properties
( j ) geometric focus effects - spherical earth approximation
Because of space limitations, the ionospheric program calculates the
field properties for only one transmitting antenna lobe at a time. The input
data required falls into three groups.
(a) Geophysical data - Transmitter and receiver locations, date, time,
daily 10 cm solar flux value, and daily planetary magnetic index Ap.
(b) Full transmitter/antenna details - Frequency, input power, antenna
gain above 1/2 X dipole and parameters of one antenna lobe including
vertical and/or horizontal directivities if required by the trans-
mitting configuration.
(c) Options - Selection of sea or land reflectivities; selection of frac-
tional E sporadic contribution.
The output information consists of the following for each F2 mode:
(a) the number of hops
(b) the azimuth
(c) the vertical angle of arrival
(d) the root-mean-square incident field computed using the semi -empi r ical
model
(e) the limiting polarization ratio (vert ical -to-horizontal ) for two lim-
iting s i tuat ions--no fading and dominance by fading.
In setting up our computer programs we have made a synthesis of a variety
of sources of geophysical, aeronomical , and radio engineering information. A
number of empirical parameters for which no direct evaluation could be ob-
tained from available physical measurements were set (by trial and error)
using direct field strength measurements of Radio Japan (NHK) , WWV , CHU, and
Radio Ankara made at Geneseo, New York. These were previously obtained as a
part of our solar eclipse propagation studies (Mei«el et al . , 1976).
As illustrative tests of the ionospheric simulation program, we present
here results for three paths for which quantitative data were provided at our
request by Radio Canada International, Radio South Africa and the
Osterreichischer Rundfunk.
(a) Meyerton, (Johannesburg, South Africa) to Ottawa, Canada - May 8-10,
1975
(b) Daventry, (United Kingdom) to Honeydew, (Johannesburg, South Africa) -
Aug. 22-25, 1976
(c) Moosbrun, (Vienna, Austria) to Geneseo, (New York State), U.S.A. -
May 08-31 , 1976
Indirect signal evaluations of all ORF transmissions for 1976 based on
detailed reception data were also made available to us together with exten-
sive receiving antenna data but these cannot be fully evaluated until the
D2 - 33
receiving station program is completed.
As might be expected the most important conceptual uncertainty involves
the specification of the polar absorption and its correlation with solar and
geomagnetic data. The role Es plays in altering signal levels on some paths
is likewise uncertain.
Because of memory space limitations, no major conceptual revisions can be
contemplated and certainly no further major additions are possible. However,
in the area of parameter refinement several items are of immediate interest:
(1) Better definition of D layer and auroral zone absorption and its de-
pendence on geomagnetic index - observations of Radio Japan (NHK)
will cont inue.
(2) Better definition of the solar cycle dependence of the properties of
the geomagnetic index, in an effort to clarify what constitutes "av-
erage" or "normal" conditions.
(3) Definition of a daily E sporadic index which can be used to predict
the average path Es contr i but ion--a parameter which functions as the
F,. or Ap index is being sought.
In spite of the theoretical simplifications and the uncertainties in par-
ameter values, we feel that the minicomputer program in its present 8K form
adequately simulates ionospheric radio propagation. To demonstrate this we
present results for several "problem" propagation paths. Other tests are
planned in the future in conjunction with the receiver site program.
RESULTS
First, we considered the North American transmission of Radio South
Africa using field strength measurements made at the Stittsville (Ottawa)
Receiving Station of Radio Canada International. The original observations
are given in the first table. For prediction purposes we adopted the follow-
ing mean parameters.
Transmitter: Long. -28? 1 , Lat. -26?6 (Meyerton, South Africa)
Receiver: Long. +76?0, Lat. +45°5 (Stittsville, Ontario, Canada)
Date: 1975 May 8 2 S00 MHz Solar Flux = 70 («F10)
Time: 2 300 U.T. (GMT) Ap Magnetic Index =15
Frequency: 9.5 MHz Power: 250 kilowatts
Beam Elevation Angle: 7.5°
Half-Power Full Width: 7°8 (vertical)
26° (horizontal)
Gain: 20 dB over isometric dipole
Azimuth: 300° Sea Water Reflection
Observed Mean Field:
2300 GMT = 16 yV/m maximum <E> - 100 uV/m
<E> 3 days = 26 yV/m minimum <E> - 0 yV/m
D2 - 3k
FIELD INTENSITY MEASUREMENTS of RADIO SOUTH AFRICA (NORTH AMERICAN SERVICE)
9525 kHz
1975 May 8, 9, 10 - 2230 to 2320 GMT
Measurements taken at five minute intervals, expressed in dB/uV/m and
yV/m.
MAY 8
MAY
9
MAY
10
Fio " 71
F10 =
69
F10 "
69
Ap = 13
Ap =
17
Ap =
17
Low Normal
Below Normal
Low No
rmal
SS No. Daily
> 0
SS =
0
SS =
9
Power
Power
Power
T
ime (GMT)
dB/yV/m yV/m
dB/yV/m
yV/m
dB/yV/m
yV/m
2230
30 31.6
15
5.6
40
100
35
33 M».7
12
3.98
38
79.4
40
38 79.4
16
6.31
34
50.1
45
36 63.1
16
6.31
25
17.8
50
36 63.1
10
3.16
23
14.3
55
30 31.6
14
5.01
20
10.0
2300
31 35.5
17
7.08
15
5.62
05
32 39.8
17
7.08
9
2.82
10
34 50.1
17
7.08
7
2.24
15
37 70.8
18
7-94
9
2.82
20
36 63.1
23
14.3
7
2.24
25
20 10.0
9
2.82
nil
nil
30
16 6.31
11
3.55
nil
nil
<E> = 50.2
<E>= 6.2
<E> = 22.1
Measurements were made with Stoddard F.I. -Meter model NM-25-T.
WWV recordings were made on C-60 cassette from 2310 to 2320 GMT each
day.
D2 - 35
Summary of Predictions
Since the prevailing Es parameters are not known, three conditions
Es = 0, .25, and .5 have been assumed in the calculations.
Es = 0 RSS* = 104 yV/m f£ = f£
Es = .25 RSS = 33 yV/m fE = fE + 1.25 MHz
Es = .50 RSS = hO yV/m fE = f E + 2.5 MHz
"RSS = root-squared-sum over all active modes
The Es parameter used here is the fraction of 5 MHz that the Es criti-
cal frequency is above the ordinary E-layer critical frequency. This
parameter is not standard but will be used in future simulation prog-
rams until a standard Es parameter is developed.
If Rayleigh fading statistics are assumed, the upper decile is 1.2 x RMS,
the median is 0.8 x RMS, and the lower decile is 0.4 x RMS. Comparison of
the individual values or the means shows the best agreement only if there is
significant Eg present (fE ^_ f E + 1.25 MHz). Since Es is usually on the
rise during May, it is not unreasonable to postulate that some Es is present
on all three test days.
As a second test, we chose the north-south United Kingdom/South Africa
path using the early morning transmission of Radio Canada International
(Daventry relay station) as monitored at the RSA receiving station at
Honeydew (Johannesburg). The solar aspect in the August period was similar
to the May period but the direction of propagation was reversed. Following
the same format as above:
Transmitter: Long. +1?1, Lat. 52? 3 (Daventry, G.B.)
Receiver: Long. -27?9, Lat. -26?2 (Honeydew, R.S.A.)
Date: 1975 Aug.
23
^10 = 69
Time: 0700 U.T.
(GMT)
Ap =18
Frequency : 11.7 MHz
Power: 100 kw
Beam Elevation Angle:
7°
Half -Power Full Width:
7?8 (vertical)
26° (horizontal)
Gain: 20 dB
Azimuth: 170° Land
Reflect ions
Observed Fields:
R.S.A. 1976 Aug. 22-25 0620-0640 GMT ^5 yV/m
0700-0720 GMT ^2.5 yV/m
0740-0800 GMT ^2 yV/m
[There was considerable interference from a Russian trans-
mitter on all days. The field measurements refer to values
when the Russian station faded out.]
D2 - 36
R.C.I. Technical Monitor - SIO (Signal strength, interference,
overall merit) Reports - Inverted "L" NW-SE
1976 Aug. 2^-28 S = 0 to S = 2 <E> 3 yV/m
1976 Aug. 31-Sept. 3 S=0toS=2 0<E<20 yV/m
Summary of Predictions
As was done previously, we generated RMS field values at three Es
conditions Es = 0, .25, and .5 representing fE = f^, fE = fE + 1.25 MHz
and fF = fF + 2.5 MHz. s s
cs
Es = 0 k yV/m = RSS*
Es = .25 5 yV/m = RSS
Es = .50 6 yV/m = RSS
-RSS = root-squared-sum over all active modes
Once again the agreement of observation within the limits of Rayleigh
statistics must be considered satisfactory.
Next, measurements of the Austrian Radio (ORF) North American transmis-
sions made by D. Meisel using an inverted trap dipole antenna were analyzed.
These measurements are not as good as the previous ones because of the un-
certainties of ground effects at the receiver particularly at 6 MHz. How-
ever using plausible attenuation assumptions, at least reasonable limits may
be placed on the incident field values. The observations are gathered in a
second table. The assumed parameters are:
Transmitter: Long. -16?5, Lat. +^8?0
Receiver: Long. 77°8, Lat. +kl°. 7
Date: 1976 May 19 F10 = 71
Time: 0010 U.T. (GMT) Ap = 7
First Frequency: 9.8 MHz Power: 100 kw
Beam El. Ang. = 14° Half-Tower Full Width: 10?5 (vert.)
Gain: \k.5 dB 10?5 (horz.)
Azimuth: 303° Sea Reflection
2nd Frequency: 6.2 MHz Power: 100 kw
Beam El. Ang. = isotropic Half-Power Full Width: - vert.
Gain: 11 dB 50° (horz.)
Azimuth: 303° Sea Reflection
The F1Q and Ap values given are interpolated from the daily values for
the appropriate GMT of observation. Since the Austria-North America path is
"trans-auroral" the magnetic field control of the signal strength is consid-
erable as is demonstrated by comparing the minicomputer results for "average"
conditions (F = 72, Ap = 10) with those prevailing at the time of the ORF
transmission and our observations (F = 71, Ap = 7) •
D2 - 37
E-sporadic
Freq (KHz)
RSS (Ap = 7)-
RSS (Ap = 10)*
Es = 0
9770
370 yV/m
230 yV/m
6155
130 yV/m
70 yV/m
Es = .25
9770
350 yV/m
230 yV/m
6155
140 yV/m
70 yV/m
Es = .50
9770
410 yV/m
270 yV/m
6155
170 yV/m
80 yV/m
"RSS = root-squared-sum over all active modes.
The agreement for both frequencies is satisfactory within the limits set by
Rayleigh statistics.
FIELD INTENSITY MEASUREMENTS of 0RF AUSTRIAN RADIO (NORTH AMERICAN SERVICE)
(a) 9770 KHz - Inverted Dipole - SPR-4 Drake Receiver
1976
GMT
Fin
Ap
Input
MEAN-E*
May 08
0020
69
11
150 yV
110 yV/m
14
0120
72
4
1000
770
14
2319
74
4
150
110
15
0051
74
4
300
220
15
2345
76
5
600
460
17
0053
75
4
600
460
25
2355
68
7
300
220
29
2356
66
16
50
40
31
2349
67
10
300
220
lean 19
0015
71
7
RMS = 36(
) yV/m
-Based on pattern recal ibrat ion 4/15/77 and 0° to 30*
range on the angle of arrival.
(b) 6155 KHz - Inverted Dipole - SPR-4 Drake Receiver
1976
GMT
Fin
Ap
1 nput
MEAN-E*
May 08
0020
69
11
300 yV
80 yV/m
14
0120
72
4
1000
260
14
2319
74
4
300
80
15
2345
76
5
300
80
17
0053
75
4
60
15
25
2355
68
7
70
30
29
2356
66
16
70
30
31
2349
67
10
100
30
Mean 20
0010
71
8
RMS = 10(
) yV/m
-'•Based on pattern recal i brat ion 4/15/77 and 0° to 30'
range for the angle of arrival.
D2 - 38
In order to check the program reliability at the higher shortwave fre-
quencies as well as investigate the seasonal behavior of a t ransequator ial
path, we generated predictions for the Canada-South Africa path at 1900 GMT
for F10 = 70, Ap = 10 and for June 15 and December 15. Frequencies of 17.8
and 15.3 MHz were assumed and the known RC I antenna patterns were used. The
results for Es = 0 and receiver coordinates of lat. -28, long. -25 were:
Jun 15
17.8 -> 160 yV/m
15.3 ■+ 200 yV/m
Dec 15
17.8 ■+ 650 yV/m
15.3 + 710 yV/m
In June, the field is contributed mainly by lowest mode (arrival angle less
than 1°) and therefore the effective incident field will be considerably less
than the amounts quoted. A summer (N. Hemisphere) fade-out is predicted by
the simulation program and is in accord with past reports by RC I monitors.
However, without an analysis of the receiving antenna pattern or without
quantitative field measurements, it is difficult to assess how good such
agreement really is. Further comparisons of other RC I or 0RF paths will be
postponed until the receiver program is available. Likewise propagation at
lower shortwave frequencies remains to be explored. Although there is no
reason to suspect that a computation failure would occur, the program has
yet to be tested for frequencies below 6 MHz. Since a full polarization cal-
culation is performed, however, no difficulties down to about 2 MHz are ex-
pected.
Extensive measurements at 15 MHz have been obtained using Radio Japan
signals, but since some of these have been used for parameter adjustment they
cannot properly be considered independent tests. Limited tests at higher
frequencies have also been carried out and these are continuing in connection
with further refinement of the F2 critical frequency algorithms. Once the
receiving station program is finalized it will be possible to predict actual
received total voltages directly and thereby refine the reception report com-
parisons considerably.
ACKNOWLEDGEMENTS
We gratefully acknowledge the contributions of the following people and
organizations to this project. K. Kinsey, State University of New York,
Geneseo, N.Y., for important FOCAL modifications; the Physics and Astronomy
Department, SUNY, Geneseo, for the extended use of the PDP-8/L computer and
associated equipment; J. R. Kearney, Transmission and Reception Research
Department, South African Broadcasting Corporation for the Radio Canada
International (Daventry, UK) measurements; Josef Jaschek and Herbert Kuhnle
of the Austrian State Radio (0RF) , Vienna, for details of their antenna char-
acteristics as well as extensive SINP0 report statistics; C. Uitzinger of
Johannesburg, South Africa, for reception data bracketing the Daventry test
period; E. I. Loomer, Division of Geomagnetism, Department of Energy, Mines
and Resources, Ottawa, Canada for important historical geomagnetic data;
the Canadian Broadcasting Corporation for making staff and equipment avail-
able for this project; and Judy Worden for particular care in typing the
final copy of this paper as well as the many preliminary drafts.
D2 - 39
REFERENCES
Central Radio Propagation Laboratory (19^8): Ionospheric Radio Propagation.
NBS Circ. kG2 , U.S. Dept. of Commerce.
Davies, K. (1965): Ionospheric Radio Propagation. NBS Monograph 80, U.S.
Dept. of Commerce.
Haydon, G. W. , M. Leftin, and R. K. Rosich (1976): Predicting the Perform-
ance of High Frequency Sky-wave Telecommunication Systems. Office of
Telecommunications Report OTR-76-102. —
Leftin, M. (1975): Ionospheric Predictions, Vol. 1. Office of Telecommuni-
cations Research and Engineering Report 13, OT-TRER 13-
Meisel, D. D. , S. B. Duke, N. Goldblatt, and R. Agugl ia (1976): Solar eclipse
effects on HF and VLF propagation. J. Atm. and Terr. Physics, Vol. 38,
^95-^99.
Ostrow, S. M. (1962): Handbook for CRPL Ionospheric Predictions. NBS Hand-
book 90, U.S. Dept. of Commerce.
Roberts, W. M. , and R. K. Rosich (1975): Ionospheric Predictions, Vols. 2,
3, and h. Office of Telecommunications Research and Engineering Report
13, OT-TRER 13, U.S. Dept. of Commerce.
D2 - ^0
A SIMPLIFIED COMPUTER METHOD FOR LONG-TERM
CALCULATION OF HF SKY-WAVE CIRCUITS
by: Armel A.E. Picquenard
Professor, Instituto Tecnologico de Aeronautica - ITA
Centro Tecnico Aeroespacial - CTA
12200 Sio Jose dos Campos - SP, Brazil
and: Eurico Rodriques de Paula
Research Assistant, Instituto de Pesquisas Espaciais - INPE
Conselho Nacional de Desenvol vimento Cientffico e Tecnologico - CNPq
12200 Sao Jose dos Campos - SP, Brazil
When planning a new HF station (Broadcast, AFTN, Coastal station,
etc.), the frequencies, transmitter power, and antennas, must be
selected to supply the required service during 10-20 years.
Consequently, previsions for the signal-to-noise ratio must be
calculated for maximum and minimum solar activity, for various months
of the year, for various hours of the day, and for the available
frequencies, hence being interesting that the computation time be
short.
After discussing most of the proposed computational methods,
and evaluating the influence of various parameters, a simplified
program has been developed, for the case of Brasil, and for short
and medium ranges, till some 4,000 Km. In this case, in Brazil, the
geomagnetic latitude is low, simplifying the problem.
Computational time, including signal-to-noise calculation, and
for a complete solar cycle, i s 3 " 3y minutes for three frequencies,
with the B-6700 Burroughs computer.
1. INTRODUCTION
The program described in this paper is intended to supply the
necessary information to the designer of HF radio stations, such as
tropical wave or HF broadcast stations, airport stations, costal stations,
etc.
An analysis of this type of problem has been made by Haydon et al.,
19b9, in a qualitative way. Our aim will be to transform those ideas in
numerical values, to allow the designer to select frequencies, transmitter
power and antenna types.
As the main factor of the service grade is the signal-to-noise ratio,
D2 - k\
the program must compute the signal received power as well as the mean
atmospheric noise power, which in Brazil is very high and is, generally, the
dominant type of noise.
The transmitting stations will remain in operation during 10 to 20 years,
therefore, calculations must be made for the extreme values of the Wolff
number, stated in R^2 = 10 and R12 = 110 respectively. For both values, the
months of March, June, September and December are regarded as typical ones
for the grade of ionization and for the atmospheric noise. Each of them is
examined, and for each of the referred month calculations are made for each
even hour (UT) . If we study the circuit in 3 frequencies, we will need 288
calculations, hence the interest in having a fast program.
From another side, sophisticated programs are rather disappointing
(CCIR, 1978b), so we can question the advantages of such sophistication,
which requires a very extensive use of "loops", due to "cut-and-try"
processes. This is peculiarly put in evidence in the 2nd CCIR Method (CCIR,
1978a), and increases the computation time very much.
Based on the above considerations, we attempted to build a program
retaining only the strictly indispensable calculations to reach a reasonable
accuracy, and without "loops". For this purpose, we have discussed the
possible influence of the parameters involved, as will be explained later
(item 2) .
Another important consideration has been that more than 30% of the HF
circuits installed in Brazil are less than **,000 Km lone, and, consequently,
remain in low geomagnetic latitude. A circuit of rather short length means
less propagation modes to be examined, and a low geomagnetic latitude
permits the adoption of a constant "system excess loss" (CCIR, 1970), thus
saving some computation. Consequently, we decided to limit our program to a
length of *+,000 Km.
2. BASIS FOR OUR PREDICTION TECHNIQUE
The next point has been to discuss the actual importance of the
computational processes used in the former methods (CCIR, 1970; Haydon and al.
197.6; Laitinen and al., 1962; Lucas and al., 1966) , and the grade of
influence of the parameters involved, taking into account the limiting values
they can have.
2.1. The deviation of the rays by the E-layer
In CCIR, 1970, an account is given of the deviation of the rays when
going through the E-layer. (Figure l).
With the geometry of Figure 1, using R0 = 6,371 Km, h E = 110 Km, and
making a = a£ , as suggested by Rawer, I960, we find
sin a = 0.983 cos A (1)
D2 - hi
MIDDLE POINT OF
THE TRAJECTORY
Fig. 1 - GEOMETRY FOR THE DEVIATION BY THE E-LAYER
Putting Z for the percent difference between the used frequency f and
the maximum frequency that the E layer can reflect, we can write:
U = 1SL
fnE sec a
1
1 + 0.001Z
(2)
We can now calculate B versus A and Z. The result of this calculation is
given in Figure 2.
As it is very difficult to use departure angles A < 5°, and as for Z < 1
we are very near of the reflection by the E-layer, we conclude that 3 wi 1 1 be
always very small, and that we can neglect it in subsequent calculations.
It seems that the CCIR has reached the same conclusion, as CCIR, 1978a,
does not more mention deviation by E layer.
2.2. Influence of h'F,F2 on the calculation of signal received power
The. virtual height of reflection by the F,F2 layer depends on the
frequency and on the geographic position of the reflection point. If we take
into account the variation with frequency, the resultant computation is
D2 - ^3
Fig. 2 - DEVIATION 3 VERSUS A AND Z
rather complex (CCIR, 1970; CCIR, 1978b). On the other hand, as we limit our
circuit to a length of ^,000 Km, the reflection points in the case of the
2 x F mode, cannot be more distant than 2,000 Km, which limits the variation
of h'F,F2, between these points.
The variation of h'F,F2 has two consequences: a variation of A, and
hence of the gain of the antenna and, correlatively, a variation of the
incidence angle on the D-layer, modifying the absorption. We shall examine
the possible values of both effects.
2.2.1. Influence of h'F,F2 on A
With the geometry of Figure 3, we obtain, for the case of 1 hop on
the F,F2 layer,
dA
1
sin 6
dh'F»
1 +
h'F2^2
- 2
1 +
h'F2>
(3)
<o J
COS 0 + 1
If we take R0 = 6371 Km and h'F2 = 350 Km, we have
dA
dh'F2
6371
si n 0
2.1129 - 2.1099 cos
CO
Differentiating for 0, we find that the maximum of dA/dh'F2 is reached for
0 = 3,05° (680 Km, value in agreement with the already published graphs) and
D2 - kk
that:
dA
Fig. 3 " GEOMETRY FOR 1 HOP ON THE F-LAYER
= 0.0799° per Km
Ldh'F2J Max
This gives us ± 8° for a variation of ± 50 Km of h ' F2 •
In the case of 2 hops on the F,F2 layer, we shall have the geometry of
Figure h.
Let us put hg = (hj + h2)/2 and h1 = (h2 - h ^ ) /2 , and assume that
h' << hg, using the subscript 0 for the values of the variables when h' = 0,
and making A' = Aq - A.
Aftersome approximations on the trigonometric functions, we find the
following equations:
- R0 A1 sin A0 = (Rq + h0 - h')(<J>i - <J>o) cos <J>0 - h' sin <|>0
= (R0 + h0 + h ' ) (4>2 - 4>o) cos <J>o + h' sin $0
(5)
By means of these equations, and using again the geometry of Figure h, we
can calculate the difference A' between the true angle A and the angle Aq
calculated using hi = h2 = h0 . For R0 = 6371 Km, h0 = 350 Km, h1 = 25 Km
and for a total distance of 4,000 Km, we find A' = 0.00^9°.
In the same way, we can calculate the displacement 2R0 (62 - 90) of the
D2 - ^5
Fig. k - GEOMETRY FOR 2 HOPS ON THE F-LAYER
reflection point on the ground. With the same values of the data, we find
55 Km.
In view of these results, our conclusion is that we can use the mean
value, ho, of the virtual heights on both ionospheric reflection points,
instead of the true values hx and h2.
2.2.2. Influence of h' F,F2 on the absorption
The angle of incidence on the D layer is a function of the angle of
departure, which in turn varies with h'F,F2, as seen in the preceding
items. The figure 5 gives the geometry involved.
We have immediately:
sin <|>D =
Rn + h.
cos A
tan A =
'0 ' "D
(h'F2 + Ro) cos 6
(h'F2 + Ro) sin 6
(6)
D = 2 Rn 6
A <* sec (J)
These equations have been solved for h_ = 60 Km, and 250 S h'F2 < 500Km.
D2 - hS
Fig. 5 - GEOMETRY FOR THE ANGLE OF INCIDENCE ON THE D-LAYER
The results are drawn, on the graph of the Figure 6, where sec <J>D is
given as a function of D and h'F2.
SEC <t>D
Fig. 6 - ABSORPTION AS A FUNCTION OF H'F2 AND D
D2 - k7
From this figure, we can conclude that, for a variation of h ' F2 of ±
50 Km, the variation of the absorption will be of the order of ± 15 %. As
the calculation of the absorption is the weak point of all the methods, this
inaccuracy is certainly tolerable.
2.3. Conclusions for our program
From the preceding discussion, we can draw the following conclusions:
a) The deviation of the ray by the E layer can be disregarded.
b) Due to the broad radiation diagram of the HF antennas, the values
found for the error on A cannot substantially modify the gain of these
antennas, for a variation of 50 Km of h'F2.
c) In the case of 2 hops F,F2, we can use the median of both values
of h'F,F2 without appreciable error.
d) The error on the value of the absorption for a variation of 50 Km
of h'F2 can be tolerated.
e) As the variation of h'F2 with the frequency will be, in the
worst case, of the order of 50 Km, we can use, without unacceptable errors,
a fixed value of h'F2, irrespective of the frequency.
3. OUTLINE OF OUR METHOD
As already mentioned> our method is intended to calculate MUF,
signal received power, and mean atmospheric noise power for the following
cond i tions :
- R12 = 10 and R12 = 110
- Months of March, June, September and December
- Even hours in UT
3.1. Propagation modes
We consider only the following modes:
- for 0 < D < 2000 Km : 1E, 1F2, 2F2
- for 2000 < D < 4000 Km : 2E, 1F2, 2F2
The possibility of existence of each mode is determined by the
conventional method, examining the position of the used frequency in
relation with the MUFs of the layers of interest, occultation of the
F2 layer by the E layer is also examined.
We don't consider the probability of existence of the various modes,
however we calculate FOT and HPF. The signal received power is calculated
for the strongest mode.
3.2. MUF
3.2.1. E-MUF
First, we calculate the MUF(2000)E by the formulas proposed in Lucas
and Haydon, 1966.
MUF(2000)E = 3,41 + 38.^31 - 68 .071 2 + 89-97 1 3
- 70.971** + 29-51 I 5 - 4.99I6 MHz (7)
D2 - 48
wi th:
I = J(1 + 0.0037 Ri2)(cos 0.881 x)1'3 (8)
Where x is the solar zenithal angle.
For x > 102°, we take I =0. We take J = 1.
The MUF(2000)E is transformed in MUF(D)E by means of the well-known
nomogram (CCIR, 1967). No allowance is made for variations of the E-MUF
wi th time.
3.2.2. F2-MUF
The calculation of the monthly median value of F2-MUF is made exactly
as explained in the CCIR Report 3^0 (CCIR, 1967), except that the
nomogram of page 396 of the referred document has been transformed into
algebraic formulas.
Later, allowance is made for the statistical distribution of the MUF,
by calculating the values of the deciles: FOT, with a probability of 90%,
and HPF, with a probability of 10%. This is made by multiplying the monthly
median values of the MUF, as calculated above, by the coefficients given in
the Table 5.1 of CCIR, 1970.
3.3. Angles of departure
The virtual heights of reflection used are:
- for the E layer : 105 Km
- for the F2 layer : those given by (Laitinen and Haydon, 1962),
translated from a geographic map to a numerical matrix, for + 5° £ $ <- 35°
and for the even hours in local time.
Using these data, simple geometrical reasonings give the angle of
departure A for the various modes.
The angle A, for the modes F2 , allows us to calculate the skip-distance
for the E layer and for this angle. The frequency of occultation by E is now
deduced in the same way as in item 3.2.1.
3.4. Attenuation
The attenuation suffered by the waves is the sum of the free-space
attenuation along the geometrical paths, the ionospheric attenuation, and
the reflection loss on the ground.
3.4.1. Free-space attenuation
We use a method suggested by Laitinen and Haydon, 1962. First, the
attenuation A^ , in free space and for the distance on the great-circle, is
calculated. After this, the following formula, deduced from Figure 56 of the
above reference gives the complement of atenuation due to the actual path
A2 = 0.823733 10"1 + 0.808697 10"2A + 0.243386 10'2A2
- 0.^70163 10_V + 0.566952 10"6A4 (9)
D2 - 49
3.^.2. Ionospheric attenuation
This attenuation is calculated for each hop by the following formula
(CCIR, 1970; Lucas and Haydon, 1966).
A. = 677»2 sec * (1 + 0.0037 R12) [cos(0.88lX)r-3 (10)
1 (f+f Jl-9.8 + 10.2
H
Where <$> is the angle of incidence at a heigth of 100 Km. For x > 102°, the
product of the two last factors is taken as 0.1.
3.^.3. Reflexion loss on the ground
This loss is calculated as indicated in CCIR, 1970. A matrix covering
the ranges + 15° < $ <- 55° and - 90° < A < - 3*»° di scrimi nantes between
"sea" and "ground".
3- *♦.*»• Excess loss
As indicated by CCIR, 1970, an excess loss is added. For low geomagnetic
latitude, this loss is given in 9 dB by the referred document.
3.5. Noise
The atmospheric noise factor, Fam, is calculated according to
Zacharisen and Jones, 1970, and corrected for the actual passband
of the receiver, b, by the formula:
PN = Fam + 10 log10b - 204 dBW (11)
3.6. Signal-to-noise ratio
As a rule, the discrimination gain of the receiving antenna can be
disregarded, so the received power will be given by
PR = 10 log PT - ZA dBW (12)
Where Py is the EIRP of the transmitter, in Watts, and ZA is the sum of
the attenuations. This gives
S/R = PR - PN dB (13)
Provision is made for calculating the gain of the transmitting
antennas by the formulas given in Lucas and Haydon, 1966, thus deducing
the power of the transmitter, P_.
k. CONCLUSIONS
Limiting the range to 4,000 Km the area of utilization to the
Brazilian region and discussinq the type of calculation strictly needed
to remain within a reasonable precision, we have developed a straight-
forward and fast program for the calculation of the performance of the HF
circuits throughout a full solar cycle.
Comparing our results with those found by Barghausen, 1969 and by Lucas
and Haydon, 1§66 we have not found any significant difference.
D2 - 50
5. SAMPLE CALCULATIONS
Figure 7 shows the MUFs for the path Rio de Janeiro (23.00°S, ^3.50°W)
to Belem (1.50°S, 48.50°W) for R12 = 10 e R12 = 110 on December.
Figure 8 shows the signal-to-noise ratio for the same path, R12 = 10
and R12 = 110, same month, for transmitting antenna gain of 1.8 dB,
transmitting power of 1 Kw, receiver noise bandwidth of 100 Hz and
operating frequencies of 13, 15 and 17 MHz. Those curves are interrupted for
operating frequencies greater than the HPF and also for negative values of
the signal-to-noise ratio. In this figure the symbols "+" represent points
where the curves would be interruped for operating frequencies greater than
the MUF and "0" points of interruption for operating frequencies greater
than the FOT. The continuous line corresponds to 1 F2 mode and the dashed
1 i ne the 2E mode.
MUF
(MHz)
20
10
R|2 =.0
22 0
10 12 14 16 18 20 22 24
UT
MUF
(MHi) -
20
MUF - F2
E-LAYER CUTTOFF
J 1 i i i
22 0
8 10 12 14 16 18 20 22 24 2
UT
Fig. 7 ~ MUFs FOR THE RIO DE JANEIRO TO BELEM PATH FOR DECEMBER
D2 - 51
** ° * * « • M 12 M 16 IS 20 22 14 t
M 0 2 4 « 6 10 12 14 M It to tt 14 t UT
Fig. 8 - SIGNAL-TO-NOISE RATIO FOR THE RIO DE JANEIRO TO BELEM PATH FOR
DECEMBER, R12 = 10 and R12 = 110
6. REFERENCES AND BIBLIOGRAPHY
Barghausen, A.F., J.W. Finney, L.L. Proctor, and L.D. Schultz (1969):
Predicting Long-term Operational Parameters of High-frequency Sky-wave
Telecommunications Systems, ESSA Tech. Rept. ERL 110-ITS 78, Boulder,
Col.
CCIR, 1 96A : World Distribution and Characteristics of Atmospheric Radio
Noise, CCIR Rept. 322, ITU, Geneva.
CCIR, 1967: CCIR Atlas of Ionospheric Characteristics, CCIR Rept. 3^0, ITU,
Geneva .
CCIR, 1970: CCIR Interim Method for Estimating Sky-wave Field Strength and
Transmission Loss at Frequencies between the Approximate Limits of 2
and 30 MHz, CCIR Report 252-2, ITU, Geneva.
CCIR, 1978a: Draft Supplement to Report 252-2. Second CCIR Computer-based
Method for Estimating Sky-wave Field Strength and Transmission loss
at frequencies between 2 and 30 MHz, CCIR XIV th Plenary Assembly,
Doc. 6/1070-E.
CCIR, 1978b: USA. Comparison of Methods used to Compute HF Sky-wave Field
Strength, CCIR Special Preparatory Meeting (WARC-79) , Doc. P/109-E.
D2 - 52
Haydon, G.W., D.L. Lucas, and R.A. Hanson (1969): Technical Considerations
in the Selection of Optimum Frequencies for High-Frequency Sky-wave
Communication Services, ESSA Tech. Rept. ERL 113-ITS 81 , Institute
for Telecommunication Sciences, Boulder, Col.
Haydon, G.W., M.Leftin, and R. Ros i ch (1976): Predicting the Performance
of High Frequency Sky-wave Telecommunication Systems (The use of the
HFMUFES k Program) OT Report 76-102, Boulder, Col.
Jones, W.B., and R.M. Gal let (1962): Methods for Applying Numerical Maps of
Ionospheric Characteristics, Journal of Research of the NBS, Vol .66 D,
Nr. 6, pp. 6^9-662.
Jones, W.B. R.M. Gal let, and M. Leftin (1966): Advances in Ionospheric
Mapping by Numerical Methods, NBS Technical Note 337, Boulder, Col.
Laitinen, P.O., and Haydon, G.W. (1962): Analysis and Prediction of Sky-wave
Field Intensities in the High Frequency Band, Tech. Rept. 9, U.S. Army
Signal Radio Propagation Agency, Fort Moumouth, N.J.
Leftin, M., S.M. Ostrow and C. Preston (1967): Numerical Maps of Monthly
Median h'F,F2 for Solar Cycle Minimum and Maximum, ESSA Tech.
Memo. IERTM - ITS A69, Boulder, Col.
Lucas, D.L., and G.W. Haydon (1966): Predicting Statistical Performance
Indexes for High Frequency Ionospheric Telecommunication Systems, ESSA
Tech. Rept. IER. 1 -ITS A 1, Boulder, Col.
Lucas, D.L., and Harper, J.D.Jr. (1965) A Numerical Representation of
CCIR Report 322 High Frequency (3_30 MC/S) Atmospheric Radio Noise
Data, National Bureau of Standards Technical Note 318, Washington, D.C.
Picquenard, A.A.E. (197*0: Radio Wave Propagation, McMillan, London.
Rawer, K. (1960): Radio Propagation between a Space Vehicle and the Earth
in the Presence of the Ionosphere, Space Research, Proceedings of the
First International Space Science Sympos ium, Nl CE , pp. 2^5~271.
Zacharisen, D.H., and Jones, W.B. (1970): World Maps of Atmospheric Radio
Noise in Universal Time by Numerical Mappi ng , (draft) Boulder, Col.
D2 - 53
PREDICTION OF foF2 BY THE MONTHLY RAT 10 (MR) METHOD
P. S. N. Murthy C. S. R. Rao Mangal Sain
All India Radio All India Radio All India Radio
Bhadravati, India Jullundur, India Research Department
Indraprastha Estate
New Del hi -110002, India
CCIR (Geneva, 197*0 at present recommends (RED. 371-2) the use of the R12
method, or the smoothed Sun Spot Number method, for predictions up to one year
or more and the I F2 method or the Ionospheric Index method developed by U.K.
for predictions up to 6 or 7 months. All India Radio (AIR) has so far been
using the R12 method for predicting foF2. This method suffers from the
"saturation effect". Both short and long-term predictions by this method have
been shown to possess a considerable degree of error (Naismith et al , 1 962) ,
The monthly ratio (for any month and hour) is the ratio of the monthly
median foF2 for the month and hour to the corresponding value of the previous
month. The ratios are calculated for at least one sun-spot cycle or preferably
more, for any particular place. The median value of these ratios is taken to
represent the value of MR for the particular month and hour for prediction
purposes. The prediction now becomes a simple affair. One just has to take
the observed foF2 for the latest available month and successively multiply
this value by MRs of the succeeding months until the particular month for
which the prediction is required, is reached. Predictions by the MR method
are based on measured foF2 values and are free from the saturation effect.
They do not entirely depend upon solar activity and do not use the twelve
month running mean values of the index for the calculations.
Initial study on this method was done by All India Radio (AIR) in the
early sixties (Rao and Sain, 1965). The study was intended mainly to find out
the suitability of the method and was confined to noontime foF2. Madras,
Delhi and Washington, representing low, middle and high latitude stations, were
selected for the study. A more detailed investigation of the method has
recently been made for the equatorial station at Kodaikanal (Geomagnetic
latitude 0 *tVN), and the scope of the study was extended to eight hours
instead of only midday.
Points of interest in the present study are: (i) MR predictions up to
3 months, including one-month and two-month predictions, had been considered
in the earlier study, whereas every MR prediction is now for three months,
(ii) R12 values based on measured Zurich Sun Spot numbers had been utilized
earlier for prediction purposes. Now the latest predicted values of R12
(published by the Swiss Federal Observatory, Zurich) and I F2 (published by the
Science Research Council, England), which would be available for the month
for which the prediction by the MR method has been made, have been utilized,
(iii) Data collected for a considerably long period of 16 years has been
utilized for study (Radio Research Committe [India] - A Series, 1956-1972).
D2 - 51*
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D2 - 55
The study has been made for the following 8 hours of the day, namely,
00, Ok, 06, 08, 12, 16, 18 and 20 hours. Monthly ratios have been calculated
for all the twelve months and for all the years. A few typical values of MRs
so obtained are shown in Table 1. It may be seen from the table that the values
of MRs vary around a mean or median and the range of variation is generally
very small barring minor exceptions. Median values of MR required for predic-
tion purposes have been arrived at from the calculated MRs for all the years.
These are shown in Table 2.
To study the effect of sunspot numbers upon the values of MRs, calculated
MRs were plotted against corresponding values of R12. During the period under
study, R12 varied from 10 to 200. The best fit line for MRs for most of the
cases was found to be parallel to R12 plotted as the abscissa. This shows that
MRs are totally independent of sunspot numbers.
Predictions of foF2 by the three methods, MR, I F2 and R12, have been worked
out for the five years, 1956, 1957, 1968, 1969, and 1970. Percentage deviation
from measured values of foF2 have been calculated for all the predictions and
the results are summarized in Table 3. It may be seen that MR method is com-
parable to I F2 method and better than R12 method.
Table 3. Percentage of predictions within 10% of observed values
of foF2 at Kodaikanal.
Year
Method
1956
1957
1968
1969
1970
MR
70
62
65
63
68
IF2
68
61
72
70
61
R12
59
31
57
Gk
52
In an earlier study on I F2 undertaken in the Research Department of AIR,
it was observed that I F2 is affected by the "saturation effect" during evening
hours in the case of equatorial stations (for example Madras and Kodaikanal)
when the values of R12 exceed 120 and are in the range of 150 to 200. During
1956, R12 rose from 80 to 160 and it reached a maximum of 200 during 1957.
Predictions for evening hours only (16, 18, 20, and 00 Hours) for the years
1956 and 1957 were therefore picked and compared. The results are given in
Table b. It is seen that MR method gives better prediction compared to the
other two methods during periods of high solar activity for low latitude
stat ions .
Table ^4. Percentage of predictions within 10% of observed values
of foF2 at Kodaikanal (evening hours only).
__^ Year
Method T955 T957
MR~ 77 58
IF2 64 kS
R12 60 13
D2 - 56
Summarizing, the MR method is likely to become useful for making short-
term predictions of foF2. Its greatest virtue is its simplicity. All one has
to do is to take the latest observed foF2 (monthly median) and multiply this
by MRs of the succeeding months. The other point in its favor is that it is
free from the saturation effect noticed in the other two methods. The method
appears promising and deserves, perhaps, a more thorough investigation and by
different countries to assess its utility. The investigation made so far
relates to one station and for 8 hours of the day only. Further work is in
progress.
REFERENCES
Naismith, R. , H. C. Bevan and P. A. Smith (1962): Proceeding of the I nsti tui-
tion of Electrical Engineers , 109 125.
Rao, C. S. R. , and Mangal Sain (1965): Prediction of Critical Frequency of
F2 Layer., J. Institution of Telecommunication Engineers (India), Vol. II,
No. 8, pp 271-281.
D2 - 57
HF COMMUNICATION PROBLEMS AT LOW LATITUDES DUE
TO STEEP SPATIAL AND TEMPORAL GRADIENTS
D. R. Lakshmi, S. Aggarwal, P. K. Pasricha and B. M. Reddy
National Physical Laboratory
New Delhi - 110012, India
Very frequent degradation in ionosphere-supported communication
occurs at low latitudes due to large temporal and spatial gra-
dients. The dynamic situation during early morning hours and the
horizontal gradients in F-region electron density associated with
the equatorial anomaly cause unusual difficulties in the choice
of operational frequencies. The magnitude and the morphology of
these problems are discussed to keep the prediction users aware of
the conditions.
1. INTRODUCTION
The tropospheric and ionospheric communication group at the National
Physical Laboratory has been responsible for issuing predictions of the
radio environment as well as for rendering advisory services for radio com-
munication organizations in India for more than 15 years. During this
period, several problems related to HF communications, which are particularly
serious at low latitudes, have arisen. This paper describes the origin of
these problems and suggests possible reasons and remedies.
Two most serious problems are caused by (a) large local time variations
of critical frequencies (f,-^), especial ly during sunrise hours, and (b) large
horizontal latitudinal gradients in the F-region electron densities
associated with the geomagnetic anomaly. Similar problems may arise with
respect to the gradients in the mid-latitude trough region at night; however,
no discussion on this aspect is included here since this paper is restricted
to low latitude issues.
2. PROBLEMS FROM STEEP TEMPORAL GRADIENTS
The local time gradients during sunrise hours are known to plague HF
communications, particularly at low latitudes (Aggarwal et al., 1976). This
problem is extremely important in countries where the mainstay of point-to-
point communications continues to be the HF band supported by the ionosphere
Consider the following:
D2 - 58
(a) HF link operators are expected to get their frequencies cleared from the
appropriate governmental authority well in advance and it is usual
practice to fix one frequency for the daytime and another for the night-
time. The use of the night frequency during sunrise will require much
more power than is normally permitted while the frequency allocated for
the daytime will be higher than the MUF during the transient period.
(b) Point-to-point links normally use inexpensive tuned directional antennas,
and frequent change of operational frequency is deleterious from the point
of view of antenna efficiency.
(c) In case of long distance circuits in the East-West direction involving
multi-hop F-region propagation, the problem of the sunrise period will
extend to a large number of hours, because the different F-region reflec-
tion points will fall in the transient location at different periods.
Figure 1 shows the diurnal variation in foF2 for Kodaikanal and Ahmeda-
bad for winter during low solar activity. The normalized hourly percentage
changes in foF2 are shown in the lower portion of the figure. The signifi-
cance of the percentage changes is important because, even assuming that
changes in the link frequency are permitted, antenna design considerations
restrict such changes. The normalized percentage changes are calculated
using the following relation:
m i ■ (foF2), ,v ,v - (foF2),
Normalized percentage hour (X + 1) hour x .
change in (foF2), (foF2),
hour x hour x
The most important feature of this diagram is the extremely steep percentage
increase in foF2, which is as high as 230 percent at 5 A.M. for Kodaikanal.
Of course, the very low nighttime minimum values in foF2 at low latitudes
are essentially responsible for these abnormally high percentage increases.
It may also be noticed from the figure that the dusk changes are not so
spectacular, especially when the percentage changes are considered.
Figure 2 shows variation of normalized percentage changes in foF2 at
dawn for Kodaikanal and Brisbane during the years 1957 to 1 967 • The solar
activity variations, modulated by seasonal variations as the running average
sunspot number decreased from about 200 to 10, are very obvious. The magni-
tude of variations at Brisbane (Geo. Mag. Lat. 35 - 7° S) during dawn are only
marginal and show very little solar activity dependence. For Kodaikanal
(Geo. Mag. Lat. 0.8 N), however, the percentage changes are spectacularly
large and the variation with solar activity is very significant. A very
interesting feature is that during high solar activity the percentage values
are larger at Brisbane, whereas at Kodaikanal the changes are insignificant.
This figure convincingly demonstrates the seriousness of this problem at low
latitudes for medium and low solar activities. The incidence of this problem
at various stations combining seasonal and solar activity variations is
depicted in Figure 3- The data employed for this study pertains to the year
1958, representing high solar activity, and the year 19&5, representing low
solar activity. The salient features that can be observed from these histo-
grams are:
D2 - 59
_KODAIKANAL
240 -
0^200
o
LOW SOLAR ACTIVITY
DECEMBER 1965
AHMEDABAO
A
z
120'
L_ 1
—
UJ
o
80
z
<
X
40
>-
_l
cr
0
r>
\y\
o
- \
X
\
-40
-J
■ 1 i I I I l L
12 16 20 0 4 8
LOCAL TIME (Hours)
J__l l I i I l 1 i I L
Figure 1. Diurnal variation of foF2 and the corresponding normalized hourly
percentage changes in foF2 for Kodaikanal and Ahmedabad. A remark-
ably large percentage increase of 230% in foF2 for Kodaikanal at
0500 LT is an important feature to be noticed.
1. Percentage changes in foF2 are dependent on solar activity, especially
at low geomagnetic latitudes.
2. The spectacularly large changes can be observed only at Kodaikanal which
is almost on the geomagnetic equator. The changes gradually decrease
with increasing geomagnetic latitude reaching very marginal values at
latitudes around 30 and above. See Figure 3-
It may be repeated again that the main contribution for these apparently
spectacular large percentage changes at very low geomagnetic latitudes is the
very low nighttime electron densities in the F-region. However, as soon as
the sun strikes the Fl layer level at dawn, the low latitude F2 region builds
up much more rapidly than at middle latitudes. This is further accentuated
by the fact that at low geomagnetic latitudes there is a steep decrease in
foF2 even beyond midnight, bringing down foF2 to a very low value at 0^00
hours local time. This problem is less serious during the dusk hours as
may be seen from Figure 1. However, at middle and higher latitudes, gradients
during dusk hours may be as large as during dawn hours partly because of an
evening enhancement in foF2 followed by a sudden decrease after sunset
(Evans, 1965).
D2 - 60
LATITUDE
KODAIKANAL (Geogra I02*N)
(Geomag 0 8'NI
— BRISBANE
(G«ogro 27-5' S)
(Geomog.35 7'S)
Figure 2. Spectacularly large values of percentage increase in foF2
for Kodaikanal during medium and low activity periods can
be noticed here. The latitudinal dependence of foF2 changes
near dawn can be appreciated by comparing Kodaikanal and
Br i sbane.
3. PROBLEMS DUE TO LARGE SPATIAL GRADIENTS
IN THE EQUATORIAL ANOMALY REGION
The equatorial zone of approximately 30° wide centered at the geomagnetic
equator exhibits several peculiar ionospheric properties, one of which is the
large spatial gradients that affect ionospheric radio propagation in a number
of ways. The phenomenon of trans-equatorial propagation, whereby frequencies
as high as 100 MHz can be reflected by the ionosphere in trans-equatorial
paths, has been studied in detail (McCue and Fyfe, 1965; Neilson, 1966;
Bowen et al., 1968; Tao et al., 1970; Anastass iades and Antoniadis, 1972;
McNamara, 1973; Neilson and Crochet, 197*0' Several suggestions were made
about the possible mode of this propagation, for example, ionosphere-to-
ionosphere reflection such as nF2 propagation, exospheric field guided
propagation, etc. However, the problem discussed here does not concern trans-
equatorial propagation, but propagation within one hemisphere itself where
anomalous communication is possible, because of large horizontal latitudinal
gradients. For example, if we consider the anomaly peak in the northern
hemisphere to be at 1 5° N geomagnetic latitude, if a north-south HF circuit
is operating such that the reflection point is on either of the sides of
the peak and if the frequency of the link is very close to the MUF, a pecu-
liar situation arises. If the point of reflection is equator-ward of this
D2 - 61
ALMA-ATA
Geogro lot 43 2 °N
BRISBANE
Geogro lot 27 5°S
MONTHS
Figure 3. The seasonal variation of dawn enhancements at different
latitudes during both high and low activity periods. The
dawn time changes decrease with increasing latitude and
increasing solar activity.
anomaly peak, the radio waves incident on the ionosphere for the northern
circuit will continuously come across increasing levels of electron density
on two counts (a) due to the vertical gradient as the radiowave penetrates
higher into the ionosphere (b) due to the horizontal gradient as the wave
progresses in the direction of increasing electron density. On the other
hand for the same link in the return direction, the horizontal gradient is
reversed. Thus the real MUF values for the two opposite directions in the
same circuit can vary by a large margin depending on the angle of incidence
and on the magnitude of the horizontal gradient. In fact, rather frequently,
especially when the operating frequency is close to the MUF (calculated
ignoring horizontal gradients), only one way communication would be possible.
This has been one of the unusual complaints in the Indian Subcontinent.
D2 - 62
J I L
-I I 1 I l
-6-4-2 0 2 4 6
HORIZONTAL GRADIENT cELECTRONS/CmJ/m)
Figure h. The effect of horizontal
electron density gradients on maxi-
mum useable frequencies. The conse-
quences can be serious for high
angles of incidence - that is for
To understand the magnitude of this
problem, we have used the Alouette I I
data (fxF2) , so that spatial resolution
of the data can be high compared to
ground based data. Assuming simple
parabolic distribution, vertical
electron density profiles are derived
in the F2 region and the latitudinal
gradients at fixed heights are com-
puted. These horizontal gradients
along the ray path are compounded with
the vertical gradients to calculate the
change in the real MUF for varying mag-
nitudes of horizontal gradients (Lewis,
1953). Figure k shows some sample
results of the change in MUF for dif-
ferent gradients for three angles of
incidence. As expected, the shift in
the MUF increases with increasing
angles of incidence (at the ionosphere).
It has been observed that gradients
between 3 to k electrons per cubic
centimeter per meter are usually preva-
lent in the equatorial anomaly region.
Figure k is given only to illustrate
the problem and results from more
long path distances,
rigorous three dimensional ray tracing methods, which confirm this, are
beyond the scope of this paper. However, the point to be noted is that even
for modest angles of incidence such as 50° and electron density gradients of
3-5 cm-3 m-1, the shift in actual MUF is from 15 MHz to 18 MHz while in the
opposite direction the effective MUF will fall to 13 MHz. Thus, employing
a frequency higher than 13 MHz will result only in one way communication.
CONCLUSION
Very obviously, the solution for both the problems discussed in this
paper is to take these situations into account while predicting the link
frequencies. It has been found practical to get a third frequency assigned
for the dawn hours and use an antenna system with appropriate bandwidth.
Predictions of operational frequencies for North-South two way links at low
latitudes should take the anomalous gradients into account and a frequency
lesser than the reduced MUF must be used.
REFERENCES
Aggarwal , S., D. R. Lakshmi and B. M. Reddy (1976): Some problems of HF
communication at low latitudes and possible solutions. I nd ian J . Rad io
Space Phys. , 5 ! 302 .
D2 - 63
Anastass iades, M., and D. Antoniadis (1972): Time delay measurements in the
Athens (Greece) - Roma (Lesotho) VHF trans-equatorial propagation
circuit. J. Atmos. Terr. Phys . , 34:1215.
Bowen, E. D., W. J. Fay and J. L. Heritage (1968): VHF characteristics of
the transequator ial ionosphere. J . Geophys . Res . , 73:2469.
Lewis, R. P. W. (1953): The reflection of radio waves from an ionized layer
having both vertical and horizontal gradients. Proc. Phys. Soc. (Lon-
don), 66:308.
McCue, C, and D. Fyfe (1965): Transequator ial propagation: Task Bridger
introductory review. Proc. IREE Aust . , 26:825.
McNamara, L. F. (1973): Evening-type transequator ial propagation on Japan-
Australia circuits. Aust. J. Phys., 26:521.
Nielson, D. L. ( 1 966) : Oblique sounding of a transequator ial path, Spread-F
and its effects on radio wave propagation. AGARDograph, 95:467-
Nielson, D. L., and M. Crochet (197*0: Ionospheric propagation of HF and
VHF radio waves across the geomagnetic equator. Rev. Geophys. Sp. Phys.,
12:688.
Tao, K. F. Ochi., M. Yamaoka , S. Watanabe, C. Watanabe and K. Tanohata (1970):
Experimental results of VHF transequatorial propagation. J. Radio Res.
Lab. Jap., 17:83.
D2 - 64
PREDICTION OF THE CHARACTERISTICS OF A RADIO SIGNAL REFLECTED
FROM A HORIZONTALLY- I NHOMOGENEOUS IONOSPHERE AND THE RELEVANT
REQUIREMENTS FOR PREDICTION OF IONOSPHERIC PARAMETERS
S. Kerblay, E. M. Kovalevskaya, E. M. Zhulina, and L. M. Ishkova
Institute of Terrestrial Magnetism, Ionosphere and Radio Wave
Propagation of the Academy of Sciences of the USSR
Moscow Region, USSR
This report deals with the research connected with the cal-
culations and the prediction of the characteristics of radio signals
reflected from a horizontally inhomogeneous ionosphere. The methods
for estimating radio signal characteristics (MUF, hop distance,
angles of arrival in the vertical and horizontal planes) and the
prediction manuals developed in IZMIRAN are considered. The re-
quirements for accurate predictions of ionospheric parameters are
discussed.
Advances in the studies of the decameter band radio waves have resulted
in significant changes in the approach to the problem of determining radio
signal propagation conditions.
A more comprehensive prediction of the maximum usable frequency (MUF) ,
including trajectory characteristics (angles of arrival in the vertical and
horizontal planes, etc.) and time delays of particular propagation modes, re-
quires (1) a mathematical formulation that ensures sufficient accuracy for
practical purposes, artd (2) prediction of the parameters of the ionospheric
layers and the horizontal components of their gradients.
With the purpose of predicting the trajectory and temporal characteris-
tics of radio wave propagation in an inhomogeneous ionosphere, the Laboratory
of Short Radio Wave Propagation of IZMIRAN has developed methods for estimat-
ing radio signal characteristics using either predicted or measured ionospheric
parameters.
A basic method (disregarding the effects of the Earth's magnetic field
and charged particle collisions) developed by Kerblay and Kovalevskaya (197**,
1977) has been transferred to the computer and the program written in ALGOL-60
has been distributed to the communication services.
The effect of the horizontal inhomogenei ty of the ionosphere is deter-
mined from the integral values
and
/$«■•!
3n
D2
/ IS dS S 6
where 3n/39 and 3n/3x are components of the horizontal gradient of the re-
fractive index with respect to the coordinates 9 and x at the current point of
trajectory; 8 is the angular distance of the current point of trajectory in
the plane of the great circle arc between the transmitter and receiver; x is
the angular deviation of the current point of trajectory from the plane of
the great circle arc.
In the model, 8\ and 62 may be presented as
(1)
(2)
The first terms in equations (l) and (2) characterize the contribution of the
horizontal inhomogenei ty of the E layer {6^) to the integral value of the
horizontal gradient of the refractive index; the second terms define the con-
tribution of the interlayer region (<5|rp) ; the third terms determine the con-
tribution of the F2 layer (Sf2)* The characteristics of radio wave trajec-
tories (hop distance, arrival angles in the vertical dnd horizontal planes)
can be obtained by solving the set of the ordinary differential equations and
analytical expressions
=
h
3n
39
dS
+
/
SEF
3n
99
dS
+
/
sF2
3n
36
dS
=
J
sE
9n
ax
dS
+
/
Sef
3n
9X
dS
+
/
SF2
3n
3X
dS
3n
L
d6l = t£ 0+ tan2^+ tan2<f>) 2 dR
39
d62 = ^- (1+ tan2i|/+ tan2*)'2 dR
3X
,. tan (}> ,D , tan f ,D
d9j = — ^— dR dX| = ~y~ ^
L,
*2
(c +61)(1+ tan2^ cos2c{))'
tan 4 = j: ~
{n2R2 - [(c + 6X) (1+ tan2^/ cos2<j>) 2]2} 2
1 6? tantfr
tan ty = — * -
c
where <j) and ty are the angles between a geocentric radius and the direction of
the ray's trajectory in the R9 and Rx planes, respectively (R9 -L Rx) ; c is a
constant; x = X] + X2J Xj >s the angular deviation of the current point of
the ray trajectory from the R9 plane in the ionosphere; X2 '5 the same beyond
the ionosphere; 6 = 61 + 6j + 62; 6; is the angular distance corresponding
to the ray path in the R6 plane in the ionosphere; 6^ and Q2 are the same up
to the ionosphere
( K. i\ sin ♦. (9) \
8l(2) = tt/2 " <h(2) - arccos^ 1V2; ^^- J
X2 = 7T/2 - i>2 ' arccos
/R2 sin^2 \
V RE /
The subscripts "1" and "2" relate respectively to the points of the ray's
arrival to and escape from the layer; Rp is the Earth's radius; Ri(2) 's the
altitude of the lower ionosphere boundary;
D2 - 66
e. = e.E + e.EF +e.F2
X,-X1E*X,EF + X|F2.,.f '^/o,^, 0,^*0,
X. = X.F2, if
i i
8NE
ax
= o,
8X
3NEF
3X
= 0.
The total hop distance, D, the angle of ray arrival in the vertical
plane, A2, and horizontal plane, a (the azimuthal deviation of the ray), are
calculated using the formulas
d = arccos (cos x cos8) , D = R^d,
R2 sin $2
A = arccos 5 ,
2 RE
a = arctan [(sin d ctn dt - cos d cos A)/sin A],
A = I arctan (tan x/sin [arccos (cos d/cos xl }
- arctan (tan x-/sin [arccos (cos d/cos X:)]}|>
d = arccos [cos Xj cos {Q\ + 6.-)].
Figure 1 shows the designations used in these formulas.
Figure 1. Diagram showing designations used in formulas. AB, AF, AE, EH, and
BF are the arcs of great circles. AB is the arc connecting the transmission
(A) and reception (B) points. AF is the arc in the plane in which there is
the point of emission and the initial point of the trajectory in the layer.
AE is the arc of the angle between the point of the ray escape from the layer
(E) and the point of emission (A). EH and FB are the projections of the
trajectory on the plane normal to the plane of the arc AF.
D2 - 67
This method has been used to obtain the relationship between the mag-
nitude and the direction of the horizontal projections of the gradients of N
and the various characteristics of radio wave propagation. The effects of
3N/86 and 3N/3x, i.e., the longitudinal and transversal gradients of the elec-
tron density may be treated as independent. The presence of 8N/86 will re-
sult in variations of MUF and hop distance and in the trajectory asymmetry,
Aj ± A2. When the gradient 3N/36 does not exceed the values (at sunrise and
with longitude) characteristic of the regular gradients, the above mentioned
characteristics do not vary but the trajectory escapes from the plane of the
great circle and results in the azimuthal deviation, a. These factors were
taken into account when developing the methods for calculating the azimuthal
deviations in the presence of a gradient in the plane of the great circle
arc (Ishkova and Kovalevskaya, 1977).
Development of the method has made it possible to separate the effects of
gradients in different directions, permitting the effects of the horizontal
gradients and statistical variability of the ionosphere to be estimated with-
out using computer calculations. The prediction manual (Kovalevskaya and
Kerblay, 1970 contains a set of graphs which make it possible to determine
the hop distance for a given operating frequency, MUF, the arrival angles of
the radio wave in the vertical plane (elevation angles) in case of reflection
from the tonosphere with a longitudinal gradient of electron density, and
from a spherically stratified ionosphere. To determine these characteristics,
it is necessary to know the critical frequencies of the regular ionospheric
layers and their longitudinal gradients as well as the geometric parameters
of the layers using a parabolic approximation. It is possible to predict the
characteristics of radio wave propagation (using computer programs based on
the prediction manual) with the following ionospheric predictions: monthly
predictions of MUF or many-year predictions of MUF (Chernyshev and Vasileva,
1973-197*0. for determining the critical frequencies and the maps (Anufrieva
and Shapiro, 1976) for determining hmF2 and ymF2. In Figure 2 is shown an
example of D(a) from the manual (Kovalevskaya and Kerblay, 1971) for various
values of 3fo/36. The solid and dashed curves show the variations in the hop
distance, MUF, and angles A with an increasing longitudinal gradient of f 0 •
Figure 3 presents the Aj (A2) diagram permitting the determination of the de-
gree of trajectory asymmetry and the difference between the angles h\ and A2.
It can be seen from the figure that the highest values of A2 - Aj can be ob-
served near the MUF (the values of MUF are indicated by crosses in Fig. 3)
and for the Pedersen ray. When 3f0/39 = 0.75 ' 10"2 MHz/km exceeds the
median value, which often occurs at sunrise, the difference A2 - L\ can reach
8-10° for the highest frequencies and the near-maximum hop distances.
The second prediction manual (Zhulina and Kovalevskaya, 1976) makes it
possible to estimate the variations in the characteristics when the statis-
tical properties and disturbances of the medium are included. The manual
contains a set of graphs permitting the determination of the variations in
the hop distances and deviations due to the statistical nature of the iono-
sphere. The manual makes it possible not only to obtain reliable estimates
of the characteristics but also to determine the range of their monthly
variations and variations due to disturbances.
This method for calculating the characteristics of radio signal tra-
jectories has been modified for the Es layer (Kerblay et al., 1977). In this
case, the Es layer is represented by a quasf-periodic model of large-scale
structure (for more details see the report of T. S. Kerblay and G. N. Nosnova
in these proceedings), the parameters of which are determined experimentally
or on the basis of statistical predictions:
D2 - 68
D.Kfn
4000
3600
3200
2800
2400
2000
1600
1200
Figure 2. Distance versus elevation
angle. hm = 3^0 km; ym = ]k0 km; f/f0
is the relation of working frequency
to critical frequency of the layer.
N(x,y,z) - 1.2* • lO^f c2 ke *
(1 + e*Z)?
aio
"ae '
0,25
id1
MHZ-Km
-i
S> '38
--
3Jo_
" ae "
0,75-10
"MH
z-Km
,v\\
\\\
3.4
\\ V
/
J
2.8
/ 2.8
\\
>» ^^~
■^ i
vs
l
v\
^ /
20 „n
1 10
"CV
J 1
W^
■
>»>*
^
■^",,***l
J 1
•
—
—
V* 1 1
0 2 A 6
8 10
12 Sk
16 \t>
20
22
24 26 28 A
0 2 A 6 8 10 12 14 16 18 20 22 24 26 28 A°2
Figure 3- Angle of arrival versus angle
of departure. hm = 3^0 km; ym = 1 **0 km;
f/fo is the relation of working frequen-
cy to critical frequency of the layer.
[1 - k sin(27Tx/l1+<})) cos(2Try/l2+^) ]2
The model of the N-distribution is in the Cartesian coordinate system,
X, Y, Z. The Z, X, Y coordinate system for the ray path at the current point
of trajectory is transformed into the R, 9, x coordinate system using the
following relations:
R
R = Rr
z.
) = x cos y+ysiny; R*x=_xsinY+y cos y ; r» ~ ixm
The angle y characterizes the orientation of the periodical structure of N
relative to the radio path direction.
The horizontal gradient of electron density is due to its periodical
structure and the orientation of the Z, X, Y coordinate system relative to R,
9, x- The expression for the component of the horizontal gradient of re-
fraction index in the (R9) and (Rx) planes is of the following form:
in.
3X
*z
K ; e f^H-KcTC?] • Ai
f **(! + e*Z)
■F-
2[1+Kcic2]"eyz"
*z,
l£±
f(l + e*'Y
Aj = ac3C2 sin y + BciCi* cos y
cj = sin(ax+4>), c2 = cos(by+i|j), C3 = cos(ax+<J>), CI+ = sin(by+^)
2tt ■ 2tt
a = -r—, b = -t—
For the gradient 3n/89, Ai is of the form
Ai = bcjcit sin y - ac3C2 cos y.
D2 - 69
The gradients 3fc/3x and 9fc/9y are taken to be zero.
Presented below are the results of the calculations made for the param-
eters 1 i , I2, f^, K taken from values published elsewhere. The following
parameters of the Es-model were used: lj = 100 km; I2 = 25 km; fc = 2 MHz;
K = 0.5; X = 0.87 km-1; y = h5° .
Some of the calculations of signal characteristics are shown in Figures
*» and 5 in the form of the functions DCa^ and D(a2) at f = 3, 5, and 7 MHz.
D,Km
2200
1800
rVt
1400
1000
600
200
o-/*3MHz
• -J-5MHZ
*°<*\& o
r**n
A<fWfe0,
±
J L
J L
> i
0 4 S 12 16 20 2^i 28 32
Figure k. Distance versus elevation angle, Es-ref lections.
34 A#i
D,Km
2000-
9U n C a
O O
>•
o«
o -f = 3 MHz
t-f=5MHH
a-f=7 MHZ
^0°
Aoo A o
tOU- Oo °
-I 1 1 1 I I I I 1 I I I t J
0 OR l.fi 2.4 3.2 4.0 oCc
-1.6 -0 8 0 Q,R 1,6 2,4 3,2 4,0 OC°
Figure 5. Distance versus azimuthal deviation, Eg-ref lect ions
D2 - 70
It can be seen from Figure h that the inhomogeneous structure of the reflec-
tion region results in a significant variation of D for each angle Aj. The
largest variance (some 500-600 km) is observed at elevation angles near zero.
The mean mode of the variations is similar to that of the regular layers; the
only difference being the absence of a clear dependence of D (for a fixed A^
on the operating frequency and the absence of the separate branch of D (A)
for the upper angles.
In Figure 5, the effect of a significant variation of the angles a2 on
D(a2) can clearly be seen. The largest range of variations in a2 (from
-1.8° to +6.5°) is observed for small hop distances. The maximum distances
corresponding to the elevation angles of 0-A° are characterized by a lesser
variance of ot2.
It was of interest to compare (even if qualitatively) the above calcula-
tions with experimental data. The comparison was made using the measured
angles A2 and a2 for reflection from the Es-layer presented in Miya and
Sasaki (1966) for two radio communication paths (D = 1 480 and 20^0 km) in the
VHF band.
The experimental data show a decrease of the variance of ot2 with in-
creasing path length and a shift of the center of the a2 distribution, which
coincides with the calculated results. A good quantitative agreement may be
noted between the measured and calculated angles A2 for D = 1 480 km. Although
the parameters used in the calculations were not coordinated with particular
experimental conditions, in general, a quite satisfactory agreement is noted
between the calculated and measured characteristics. The conclusion may be
drawn, therefore, that the proposed method may well be used to calculate
the characteristics of the signal reflected from the E -layer.
The above prediction materials in practice set forth definite re-
quirements for the accuracy of the results obtained.
The accuracy of this method depends on a number of factors, namely, the
approximations used in the physical formulation of the problem, the method
of mathematical solution, and the accuracy of the input ionospheric param-
eters.
The first two factors (geometric-optical approximation neglecting charged
particle collisions and anisotropy* and the numerical method of solution)
introduce errors that are insignificant when compared with the errors due to
insufficient accuracy of the ionospheric parameters and, therefore, only the
latter source of the errors will be analyzed here. The analytical form is
most convenient for presentation of the N(h)-profile in calculations. Selec-
tion of the analytical N(h)-profile model, which best represents the real
N(h) distribution and is sufficiently simple to avoid undesirable difficul-
ties in calculations, is a separate task.
The propagation characteristics of the F2 layer were intercompared for
various analytical models (parabola, biparabola, linear layer, etc.) for
fixed values of hmF2 and ymF2. The differences in the hop distances (A =
constant) using a parabola (quas iparabola) , biparabolic and quadratic
"It should be noted that the effects of the Earth's magnetic field are neg-
lected when making massive calculations. There exists a version, of the pro-
gram that calculates separately the ordinary and extraordinary components,
which is used when the effect of the magnetic field is expected to be sig-
nificant.
D2 - 71
sinusoid have been found to be 200-250 km at distances exceeding 3000 km (for
the Pedersen rays and at low angles of elevation a). The differences are
much smaller at the frequencies near the MUF. In the case of a linear
(quasi 1 inear) N(h) distribution, the hop distances are significantly in ex-
cess (AD > 400 km) of the corresponding values for other distributions.
In case of the regular altitude dependence of the lateral gradient of
electron density, the differences in the azimuthal deviations of radio wave
arrival (D = constant) are insignificant with the exception of the linear
model. For the gradients of the ionospheric parameters, which are several
times the median values, the differences in a are 0.3° for the lower rays
and ^0.5° for the Pedersen rays. For gradients when the parameters are near
the median values, the differences are but hundredths of a degree. In the
linear model, such differences are much larger (a a - 1 " 1.5°). From these
results and considering that a near-linear distribution of N(h) occurs only
at individual moments in the equatorial zone, the assumption has been made
that the N(h)-profile may be presented as a combination of parabolas.
Table 1 indicates the magnitude of the error in the calculated character-
istics resulting from inaccuracies in the parameters of a layer. Because
the F2 layer has the greatest thickness and electron density and is the most
variable, the calculations for this layer are used as an example. Examined
separately will be the effects of the errors in determining the absolute
values of the parameters fg , hm, ym and their longitudinal gradients.
Errors in determining the absolute values of the parameters will result
in the following errors in the propagation characteristics. An error in the
critical frequency, 6 f 0 = 20%, leads to values of SD (at Ai = constant) rang-
ing from 100 to 700 km; the highest values have been obtained for the highest
working frequencies and for the Pedersen ray. Table 1 lists examples of the
numerical values.
Table 1. Examples
of numerical values.
3f0/3x = 0.5
• 10"2 MHz/km
SD, km a°
f/f0 A° D, km
oa
2.0 10 1900 -100 0.1 -0.05
+250 +0.2
<l.k 8 2250 -160 0.2 -0.05
+650 +0.25
Errors of the same order have been obtained for 6 ym = 40 km (hg = constant).
Somewhat smaller errors (by a factor of about 2) are due to 6 hm = 50 km
(y_ = constant). The variations in the azimuthal deviations are also largest
for the upper ray and are not appreciable for the lower ray. When the layer
parameters have been determined without error but the determination of the
gradients involved some error, the inaccuracies in the characteristics (es-
pecially the angular parameters) are much larger. These calculations are
exemplified in Table 2, which shows that, as 5 fg /&x and 6 hm/6x vary, a is
changed by 0.1-0.8°. This is in excess of the values of 6a presented in
Table 1.
Therefore, not only do the requirements for accuracy of the input iono-
spheric data necessary to the calculations relate to the absolute values of
D2 - 72
the N(h) -profi le parameters, but also (to a considerable degree) to the
accuracy of the representation of 3N/36 and 3N/3x.
Table 2. Examples of numerical values.
ct°
a°
3f0/3x ' 10"2 MHz/km
3hm/3x • 10"? km/km
D, km f/f0 0.25 0.5
D, km f/f0 -1 .5 -3-0 -5-0
1000 1.6 0.2 0.4
1400 2.0 0.1 0.2
2.0 0.7 \.k
1200 1.6 0.4 0.7 1.2
1600 2.0 0.25 0.6 0.9
2.0 0.6 1.2 2.0
REFERENCES
Anufrieva, T. A., and B. S. Shapiro (1976): Geometric parameters of the F2
ionospheric layer. Nauka, Moscow.
Chernyshev, 0. V., and T. N. Vasilieva (1973-1974): Prediction of the max-
imum usable frequencies, W=10, 50, 100, 150. Nauka, Moscow.
"Collected programs for calculating the trajectory characteristics of short
radio wave propagation" (1975). Nauka, Moscow.
Ishkova, L. M. , and E. M. Kovalevskaya (1977): On the calculating method of
the characteristics of short radio wave propagation in the equatorial
ionosphere. In: Methods for Studying the Regularities of Radio Wave
Propagat ion. Nauka, Moscow, pp. 65-71 •
Kerblay, T. S., and E. M. Kovalevskaya (1974): Trajectories of short radio
waves in the ionosphere. Nauka, Moscow.
Kerblay, T. S., and E. M. Kovalevskaya (1977a): Angular characteristics of a
radio wave trajectory in a horizontally i nhomogeneous ionosphere.
Geomagn. i Aeron. , 17:671.
Kerblay, T. S., E. M. Kovalevskaya, and G. N. Nosova (1977b): On a method
of calculating trajectory characteristics of radio signals reflected from
the Es-layer. In: Diffraction Effects in Decameter Radio Waves in the
Ionosphere. Nauka, Moscow, 82-89.
Kovalevskaya, E. M. , and T. S. Kerblay (1971): Calculations of the hop dis-
tances, the maximum usable frequency, and the radio wave arrival angles
including the horizontal i nhomogenei ty of the ionosphere. Nauka, Moskow.
Miya, K. , and T. Sasaki (1966): Characteristics of ionospheric Es propaga-
tion and calculation of E signal strength. Radio Science, 1 : 99- 1 08 .
"Monthly predictions of MUF." Gi drometeoi zdat .
Zhulina, E. M. , and E. M. Kovalevskaya (1976): Calculations of the radio
wave propagation characteristics including the statistical properties
of medium ionospheric disturbances. IZMIRAN, Moscow.
D2 - 73
USING SOLAR FLUX INDEX PREDICTIONS TO FORECAST HF RADIO WAVE PROPAGATION
David Jacob Snyder
Brooklyn Col lege
1137 E. 12th St., Brooklyn,
New York 11230, U.S.A.
A technique for predicting solar flux index numbers has
been developed whereby the current solar flux cycle is corre-
lated against the previous one. A future value of the current
cycle can be predicted by the following formula:
yp = (r (sy/sx)) (x-x) + y,
where r is the correlation coefficient, sy and sx are the stan-
dard deviations of y and x, x" and y are the means, of x
and y respectively, and yp is for long term and for short term
predictions. The reliability of this technique is discussed on
the basis of standard deviations of predicted values for both
short term and long term predictions. Predictions of high
frequency radio wave propagation based upon data compiled by
correlations of the solar flux indices against various high
frequency radio wave propagation paths are discussed. Examples
of radio wave propagation predictions based upon the compiled
data and the predicted solar flux index number are given.
1. INTRODUCTION
The solar flux index is a measurement of the overall level of solar activ-
ity. It is closely associated with the well known daily sunspot number and
may soon be preferred to the sunspot number as a measurement of solar activity.
While following the eleven year average cycle of solar activity, flux values
vary from one day to the next in association with the activity on the sun.
This activity influences the range of frequencies which will support iono-
spheric radio communications on specific circuits.
The solar flux index has been correlated with the temperature of the
ionosphere in many studies. These studies show that the temperature of the
isothermal region above the thermopause and the exospheric temperature show a
variation associated with changes in the density of the ionosphere and in the
solar flux index. The dependence of the variation of temperature on the
intensity of solar ultraviolet radiation, as characterized by the solar flux
index, apparently becomes more pronounced with increasing height.
The solar flux index measurements are gathered at the Algonquin Radio
Observatory (ARO) of the National Research Council of Canada using a reflector
of 1.8 meters in diameter, on a frequency of 2800 MHz. These radio emissions
which originate from the solar disk and from any active regions are a continu-
D2 - Jk
ation of observations which were begun in Ottawa in 1 9^+7 - Historically the
measurement taken at local noon (about 1 700 universal time) has been con-
sidered the "official" value for the day. The solar flux index is measured
in units of 1 0~^0 watts per square meter per cycle per second, and in gen-
eral, have a range from about 60 to *t00 units (Figure 1).
2. PREDICTION TECHNIQUE
A method for developing accurate predictions of future solar flux index
values based upon previous observations was employed. In no sense is it
believed that the past values are the cause of future values. Rather, some
reliable indicator which will predict future values is desired.
The Pearson product moment correlation coefficient was used in order to
employ the following two linear regression formula:
yp = (r (sy/sx)) (x-x) + J,
where r is the correlation coefficient, sy and sx are the standard deviations
of y and x; x~'and y are the means' of x and y, respectively; and yp is for
long-term and short-term predictions'.
3. BASIS FOR TECHNIQUE
The correlation coefficient (r) between the current and past cycles of
the solar flux index at 10.7 cm isn-762022 for 29 days, and 0.9125^ for
766 days,
Tests of significance which can usually be applied to correlation studies
(parametric tests) cannot be applied here because such tests fail to be appli-
cable for a time series. These tests assume that samples are drawn from a
stable and normally distributed universe, which does not exist in a time
series such as the solar flux index. Therefore, the test used was a non-para-
metric test which ignores the limiting assumptions of the parametric tests.
Such a non-parametric test is the Kendall-Mann test.
In Figure 2, the relationship between the current (designated by a
circle) and past (designated by a square) monthly averages of the solar flux
index is illustrated. When 25 monthly averages were correlated, the Pearson
correlation was 0.95^15, the Spearman correlation was 0.86692, and the Kendall-
Mann tau b correlation was 0.70000. The correlation of the whole cycle dif-
fers little from that of the monthly averages: for 766 days the Pearson r
was 0.91251, Spearman r was 0.80229, and Kendall-Man tau b r was 0.61651.
FtRure U
SOLAR «A0I0 FLUX, 10 7 CM
«UJUSI£D TO 111
|i,9<|it3r|»M{iM<|iMo|i*»i|iMi|>««4,t4|itai|i«M|iit>|iM«|iM«|i,ro|i,Fi|i,ri\,ri|i,T<|„r,|itr«|i«rr ~
Figure 1. Solar radio flux, 10. 7 cm, adjusted to I . A. U
D2 - 75
Sn
5-i
R-
Q.
cr
_i
o
Bn
Figure 2. The relation-
ship between the cur-
rent (designated by a
circle) and past (de-
signated by a square)
monthly averages of the
solar flux index.
0.0
5.0
15.0 20.0
MONTH
25. D
30. C
These correlat ions are all greater than the critical values for a two-tailed
test at the 0.01 level of significance.
*♦. RELIABILITY OF PREDICTION TECHNIQUE
The reliability of the prediction technique is illustrated in Table 1
for monthly averages and in Table 2 for dally values. The measurement of
reliability is based upon the standard deivations of predictions, using the
following formula:
a = /r(YP-Y)^/N
D2 - 76
Table 1. Standard deviations of monthly mean predictions
for July 1976-August 1978.
Month(s) Predicted in Advance Standard Deviation
1 5. 795**
2 8.6790
3 10.2336
4 10.0157
5 10.8352
6 12.3181*
Table 2. Standard deviations of daily predictions
for August 1977~September 1978.
Day(s) Predicted in Advance Standard Deviation
1 9-4011
2 9-4677
3 10.1373
4 11.6312
5 11.9235
6 12. 1 504
7 12.4472
8 12.5362
9 12.6182
10 12.7766
11 12.9796
12 13.3382
13 1 3 • 82 1 3
14 14.3113
Figure 3 illustrates the comparison of observed (indicated by a circle)
and predicted values (indicated by a square) for predictions made one month in
advance.
5. RADIO PROPAGATION CHARTS
The various solar flux indices have been correlated with the radio trans-
mission frequency, time in Greenwich mean time, and the location of the trans-
mitter and receiver, in order to predict radio wave propagation. These charts
(Tables 3a~3i) are a result of two years of collection and compilation of data.
The data consisted of the stations that dxers (individuals who listen to dis-
tant transmissions on short wave radio) have heard from the start of the
current cycle to date. An estimated 40,000 such reports have been evaluated
from many radio hobby club publications. These clubs, whose membership is
above 3,000, constitute the majority of listeners in the United States. Their
equipment ranges from simple portable radios to highly expensive and sophis-
ticated communications receivers.
D2 - 77
Figure 3- The compari-
son of observed (indica-
ted by a circle) and
predicted values (indi-
cated by a square) for
predictions made one
month in advance.
1C.D
2S.D
20.D
MCN'TH
The solar flux index of the previous day can be heard on radio station
WWV from Fort Collins, Colorado. The station is on 2.5, 5, 10, 15 MHz and
the announcements can be heard at 18 minutes after the hour. The current flux
can be estimated by the prediction technique as much as two weeks in advance.
6. EXAMPLES OF PROPAGATION PREDICTIONS
The charts can be used to accurately predict ionospheric radio propaga-
tion on any given day if the flux is known. Here are a few examples of pro-
pagation predictions made by the chart versus what was actually heard:
D2 - 78
•HOM TO PICK • SAND* BY DJVID JACOB SNYDER
FOR EASTERN NORTH AMERICA JUNE 1476 ISSUE
SFI EUROPE
1*3
1*0
1T»
172
171
170
14*
16S
SOUTH ANER1CA
6 HHI 1000-110*)
6 NHI 1000-UOO
9 HHZ 0")34-10)0
3 MHZ O0O0-01O0
11 HHZ 0100-0130
19 mi 0100-013*
3 HHI 093 0-1000
4 MHZ 033 0-0400
3 MHZ 1030-1130
3 NHZ 0200-0230
4 NHZ 0*00-0500
9 NHZ 2200-2230
19 NHZ 2200-2230
9 NHZ 2200-2230
13 NHZ 0030-0100
13 NHZ 0230-0300
4 NHZ 1130-1300
3 NHZ 103O-1130
13 NHZ 0330-0400
4 NHZ 2030-2100
13 NHZ 2200-2230
9 NHZ 2030-2100
4 NHZ 2330-0030
3 HHZ 2300-2330
4 NHZ 0300-0400
3 NHZ 2230-2300
4 HHZ 0400-0300
3 HHZ 2200-23301
NORTH AMERICA
6 HH2 1100-1300
2 NHZ 0300-0330
3 NHZ 03M-O630
4 HHZ 0230-0300
141
6
mz
0130-0200
s
NHZ
2230-
2300
21
NHZ
1630-1700
9
ml
0300-
0330
136
0
NHZ
0300-0330
137
3
NHZ
0100-0200
136
9
11
NHZ
MHZ
2230-
2200
2300
-2230
0230-0300
153
4
NHZ
0300-0330
15 1
11
NHZ
2201
-2230
15
NHZ
0000-0030
144
4
mz
00 30-
0100
146
15
NHZ
2131
-2200
146
0
mz
1130-
1200
145
21
HHZ
1630-1700
11
NHZ
0530
-0600
143 12 NHZ 1200-1230
142
141
I4t
130
3 MHZ 0930-0930
3 NHZ 0900-1000
3 HHZ 0730-0900
9 HHZ 1130-1200
11 HHZ 1030-1100
17 HHZ 0430-0900
15 NHZ 0430-0300
4 HHZ 1030-1230
2330-0130
7 HHZ 1130-1200
9 NHZ 1130-1200
13 NHZ 1200-1230
4 HHZ 2330-0130
19 NHZ 2330-0000
4 NHZ 1000-11001
2230-2300
11 NHZ 1130-1200
3 NHZ 1200-1230
4 HHZ 1130-1200
9 HHZ 2200-2300
7 NHZ 0630-0700
11 NHZ 1030-1100
19 HHZ 1130-1200
6 HHZ 0600-0630
19 NHZ 0400-0430
11 NHZ 1300-140*
19 NHZ 1200-1400
2130-2200
19 NHZ 0630-070O 3 NHZ 0330-0400
11 NHZ 0700-0730
4 NHZ 0330-0400
2 NHZ 0130-0400
13 NHZ 0430-0900
Table 3a. How to pick a band for Eastern North America June 1978 Issue
SFI EUROPE
133 11 NHZ 0130-0200
II*
124
12S
127
123 6 NHZ 0130-0400
124
122
120 19 NHZ 1600-1630
119 21 NHZ 1730IOOO
117
114
115
113 19 NHZ 230O-233*.
lie
10*
107
1**
109 6 NHZ 0O*O *loo
9 HHZ 220*-233*
13 HHZ 1*09- 1*30
104 3 HHZ ?0M> .' I >0
103 11 HHI 23M-2330
SOUTH ANtRICA
13 NHZ 0130-OZ30
4 HHZ 0100-0130
3 MHZ 0730-0600
4 HHZ 0900-0930
3 HHZ 1000-1130
19 NHZ 2230-2300
4 NHZ 0300-0400
4 HHZ 03OO-033O
4 NHZ 0300-0400
3 NHZ 0300-0330
4 NHZ 0230-0300
6 NHZ 1000-1030
3 HHZ 1*30-1100
4 NHZ 1*00-1030
19 HHZ 2210-2300
4 KHZ 0300-0400
* HHZ 0430-0900
ASIA OCEANIA
11 HHZ 2100-2200 3 NHZ 0(30-0930
0700-0730, 2000-2030
11 NHZ 2000-2030
0100-0230
13 HHZ 2330-0300
19 HHZ 2200-2230
NORTH ANER1CA
15 NHZ 0130-0230
9 NHZ 0230-0300
11 NHZ 0100-0130
3 NHZ 1130-1200
9 HHZ 1000-1030
11 NHZ 0900-0930
13 HHZ 1100-1130
0130-0200
0230-0300
9 HHZ 1700-1730
19 HHI 1230-1300
9 NHZ 2200-2300
11 mZ 0700-0630
ii mz 0400-0300
3 NHZ 1100-1130
3 NHZ 0730-1100
11 NHZ 0600-0700
12 mZ 0930-1000
13 mi 0430-0700
13 mz 0400-0430
4 NHZ I OOO- 1 »00
11 NHZ 0130-0200
4 mZ 0900-0600
06 30-0700
7 mz 0630-0700
9 NHZ 0630-0700
9 MHZ 2130-2230
4 mz 2130-2230
3 ml 2230-2300
4 mz 2230-23*0,
0230-0300,0330-
-0400,0600-06301
9 mz 2200-2230
1 MZ 2230-2300
19 NHZ 2200-2230
9 mZ 1830-2200
1 mz 2130-2210
4 mz 223O-23O0
2100-2130
3 mZ 0400-0430
4 mZ 0330-0400
0900-0930
3 mz 0400-0430
3 mZ 0900-0930
4 mz 0130-0200
0400-0400
4 mZ .'200 .100
*60*-*7**
9 mz 0900-043*
19 HHI 201O-221*
4 mi 2210-2100
13 MHZ 1*]*-14M
21 10 2200
4 mz 0100-0400
3 mz 0400-04)0
4 mi ai*a-*4** 4 mi 2210-2100 1 nhi 1100-1110
4 mi MM *»**
Table 3b.
D2 - 79
SFI EUROPf
192 II "HZ 0100-0330
09 6 mi 0333-3*00
98 5 *1 2130-2 200
SOUTH AMERICA
«. HHZ 0100-05OO
95 9 MHZ 1930-2030
9* 6 KHZ 0030-0100
02 30-0330;
9 MI 2130-2230
92 9 KHZ 2200-2230
2300-3300
11 MHZ 2330-0000
0300-0330
91
90 12 HHZ 2030-2100
88 6 HHZ 0300-0330
7 HHZ 0130-0200
11 HHZ 0600-0630
3 HHZ 213 0-2200
15 HHZ 0300-0330
6 HHZ 2330-2330
* HHZ 0400-0*30
11 HHZ 0330-0*00
15 HHZ 1 130-1200
3 MHZ 1100-1200
5 MHZ 1100-1200
7 MHZ 05C3-0530
15 MHZ 1B30-2000
9 MHZ 1000-1100
1130-12OO.1700-
1730.1800-1830
15 HHZ 2200-2300
9 MHZ 2130-220C
2300-2330:
11 MHZ 2300-2330
15 MHZ 1200-1300
2200-2230
7 MHZ 2000-2030
15 MHZ 2230-2300
9 MHZ 0000-0030
0500-0530
11 HHZ 0500-0530
9 MHZ 2130-2200
0230-0330
7 HHZ 2200-2230
9 MHZ 2200-2230
9 MHZ 1300-1330
MHZ 1000-1*00
15 MHZ 0330-0*00
11 MHZ 0330-0530
9 MHZ 1800-1930
11 MHZ 0030-0100
15 MHZ 0130-0230
1930-200
5 MHZ 1130-1200
11 HHZ 1100-1130
12 MHZ 1730-1830
7 MHZ 2100-2200
9 MHZ 2200-2230
1830-1930
11 MHZ 1700-1900
2100-2130:
12 MHZ 1230-1300;
15 HHZ 2000-2030.
0*30-0500.0200-0230
9 MHZ 1900-1930 7 MHZ 0600-0630
11 MHZ 1500-0000
15 HHZ 0130-0200.2330
-0100.0*000-0530:
17 MHZ 0100-0230
AFRICA
11 MHZ 1900-1930
* HHZ 2130-2300
0*00-0*30.0530-0630
9 MHZ 2030-2100
6 MHZ 2030-2100
* HHZ 1200-1230
0300-
-0330.0*30-0600
11 HHZ 1900-1930
9 MHZ 0200-0230
0300-0330
3 MHZ 0500-0600
* HHZ 2300-2330
11 HHZ 1530-1630.
1830-0030
9 HHZ 0600-0630
11 MHZ 1900-1930
6 MHZ 2230-2330
7 HHZ 0600-0630
* MHZ 2130-2200
0600-0630; 7 HHZ
0530-0630;
15 HHZ 1800-1900
5 MHZ 0*00-0*30
6 MHZ 0300-0330
7 HHZ 0*00-0*30
11 HHZ 2300-2330
9 MHZ 0*30-0530
11 MHZ 2000-2030
22 30-2 330
NORTH AMERICA
11 HHZ 0230-0300
15 MHZ 22C0-2230
3 MHZ 0*30-050
9 HHZ 1*00-1*30
5 HHZ 2200-2300
Table 3c.
SOUTH AMERICA
OCEANIA
* MHZ 0900-1330
6 MHZ 0030-0100
11 MHZ 1100-1200
12 HHZ 1230-1300
1830-1900
15 HHZ 1400-1*30
6 MHZ 0200-0230
7 MHZ 0200-0230
9 MHZ 0200-0230
U MHZ 0200-0230
9 MHZ 0000-0030
0130-0200
2130-2200
11 MHZ 0130-0200
12 MHZ 2100-2130
9 MHZ 2130-2230
2330-0030
3 MHZ 1030-1130
3 MHZ 1130-1200
MHZ 0100-0130
MHZ 0200-0230
HHZ 0000-0030
6 MHZ 0000-0 330
09 00-0930
12 MHZ 1130-1200
* MHZ 2330-0000
0100-0203.0*30
-0500.0600-0700:
6 MHZ 1100-1130
11 MHZ 2300-2330
* HHZ 07*0-0800
11 MHZ 0200-0230
15 MHZ 2100-2130
22)0-2300
ASIA
2300-0000
11 MHZ 1030-1100
12 MHZ 1700-1730
15 MHZ 0300-0330
17 MHZ 0300-0330
7 MHZ 1230-1300
9 MHZ 05 30-0830
10 MHZ 1100-1130
11 MHZ 1200-13000
15 MHZ 1200-1230
17 HHZ 1530-1600
6 MHZ 2230-2300
9 MHZ 2200-2230
11 MHZ 1030-1100
1330-1*00
9 MHZ 1330-1*00
2200-2230
11 HHZ 1700-1800
1330-1*00
7 MHZ 0300-0330
0*00-0*30
9 MHZ 2030-2100
11 HHZ 1230-1300
15 MHZ 2330-0100
0200-0300
* MHZ 1130-1230
7 MHZ 0500-0530
1100-1200
» MHZ 1930-2030
2200-2300.0200
02301 11 MHZ 1130
-1200.2109-2130
15 MHZ 0200-0230
2000-2030
5 MHZ 1130-1300 *MMZ 08)0 0900
7 MHZ 0*30-0500 6 HHZ 0530-0600
9 MHZ 1000-1230 7 MHZ 0800-1100
1930-2300.0*00 9 MHZ 0330-0600
-0*001 II NMZ 1700 11 MHZ 0600-0630
-1730.2200-2230
0100-0130.1130-
12001 13 MHZ 23)0-
AFRICA
NORTH AMERICA
15 MHZ 0*00-0500
» MHZ 1530-1530
7 HHZ 0800-0630
11 MHZ 1630-1730
15 MHZ 0*00-0*30
11 MHZ 0*30-0500
3 HHZ 0*00-0*30
* MHZ 0*00-0700
5 HHZ 2230-2300
6 HHZ 2230-2330
9 HHZ 0*00-0*30
11 MHZ 2030-2100
3 MHZ 2330-0000 9 MHZ 1230-1300
* HHZ 0700-0730.2230
-0000; 5 MHZ 2130-
000: 7 MHZ 0230-0300
0*00-0*30.0730-0800
9 MHZ 2200-2230
11 MHZ 1500-1700.
0200-0230:
15 HHZ 1500-1700
* MHZ 2000-2230
2330-0000
9 MHZ 2130-2200
3 HHZ 0130-0200
3 MHZ 0000-0030
0200-0330
9 MHZ 1*00-1500
5 MHZ 2030-2100
6 HHZ 2230-2330
9 MHZ 2230-2330
15 MHZ 1300-1330
1800
-1900.1930-2030
3 MHZ 2200-2300 3 MHZ 0000-0300
* MHZ 2230-2300
0600-0630
6 MHZ 2100-2330
7 HHZ 2300-0030
0*30-05001 9 MHZ
0030-0100,02 30-0330
0*00-0*30.1630-1730
11 HHZ 1900-2030
15 HHZ 2100-2200
0200-0230
21 MHZ 1330-1*00
3 MHZ 0630-0700
* MHZ 2000-2300
0300-0330.0*00-0600
06 30-0700
5 MHZ 0*30-0300
06 30-0700
6 MHZ 0630-0730
7 MHZ 0*00-0*30
0600-0730
9 MHZ 0330-0600
11 MHZ 2300-2330
3 MHZ 0*30-0500
0530-06001 * MHZ
02 30-0300.0*00
0330.2000-20)01
5 MHZ 0*30-0500
7 MHZ 0*00-0*30,0330
0600: 9 MHZ 1800-
1900.1930-2000
» MHZ 0300-0330
0630-0700
3 MHZ 03O0-O600
15 MHZ 2000-00)0
Table 3d.
D2 - 80
sm Europe
3 ml 0490-0)00
6 mZ 0200-0230
0*00-0930
9 mi 0000-0030,
0130-0200:
11 MHI 1630-1730
0100-0330
IS MMt 1130-1200
1430-1030
IT KHZ 1230-1300
13 30-1*00
21 HH2 1700-1730
3 MI 0*00-0430
6 MHZ 0300-0330
7 mi 0100-0430
9 ml 1930-2000
223O-23OO.03O0
03301 11 KHZ 0000
0030.0100-0400
SOUTH AURIC*
4 MHZ 2330-0000
0300-0330.0300
0)00-0330
3 MHZ 0700-0730
11 MHZ 0000-0030
0100-0200
13 MI 2100-2200
1230-1400
4 MHZ 0400-0430
3 MHZ 1030-1130
11 MHZ 2100-2200
* MHZ 0330-0400 3 KHZ 0400-0430
0430-0700 4 MHZ 0200-0230
* MHZ 0000-0200 0330-0*30
1030-1900 11 MHZ 2330-0230
11 MHZ 1300-1330
2130-2200.0300
-03301 19 MHZ 1230
1300.1430-1300
1*00-1*30
2200-2230
MM
0100.0400-0430
4 (HZ 1130-1230
0030-0130,0230
-03301 * MHZ
0300-0330,0000
093OS 7 MHZ 0230
0330; 9 MHZ 1200
-1300,1*0?-1T30
1(00-1(30, 1900
-1930,2100-2130
0900-1000,1030
-1100: 11 MH2
1030-1100,1200
-1300.1600-1730,
1930-2030
19 MHZ 2200-2230
2330-023 0,0300-0330
17 MHZ 1030-1100
3 mZ 21 30-2200
4 MH2 1130-1200
2030-2 13 0; 9 MHZ
1600-1630,2030
21301 6 mi 2100
21301 7 WZ 0430
0900; 9 ml 1000
-1030,1100-1130
1200-1430,1600
1630,1900-1930
2000-2030,2100
2130,0000-0030
0200-03001 11 NH2
0930-1000, 1330-1300
1730-1(00.
2330-0200;
12 MH2 1930-1630
19 MHZ 2300-0130
0200-0300, 1200-
1230,1600-1630;
17 MHZ 1600-1630
0200-0300; 21 MHZ
1300-1330.1400-
14301
4 mZ 1030-1330
0400-0430
T mZ 1030-1300
iaoo-1900; 9 mz
1100-1 130, 2030
2100,2130-2230
0130-0300,0900
0930; 11 HH2 1100
1*00,1630-1900
2030-2200,2330
0000,0100-0130;
19 MHZ 1930-2130
AFRICA
WORTH AMERICA
3 mz 0400- mm
4 MHZ 0900-1330
7 mZ 070O-0730
9 mz 0*30-0700
ii mz 0400-0430
0*30-0730
13 mz 0100-0430
3 MHZ 0900-1000
1030-1130
1200-12300
6 MHZ 0630-0700
ii mz 0100-0130
13 mz 1900-1930
0100-0430
3 mZ 1230-1300
11 mz 0900-0700
19 mZ 1(30-1900
0200-0230,
0300-0930
2300-2330,0330
-04001 11 mi 1900
-1700,1900-2230
19 MH2 1900-2000
3 mi 2130-2200
03 30-0400; 4 MHZ
2030-2100.2200
2230.0200-0430,
0700-0730
3 mZ 0330-0430
7 mz 2130-2200,0400
-0900; 9 mz 1(30
-2130,2330-0300
0300-0330; ii mz
1900-1700,1730
-1030,0930-0630
19 MHZ 1T0O-2000
2100-0030
17 MHZ 1700-1730
3 mz 0230-0330
0400-0930
9 MHZ 0400-0430
11 mz 1230-1330,0000
0000-0030
0100-0130
3 mZ 0600-0630
0330-0900
4 mZ 2100-2200
2230-2300,0330
-0930,0600-0700
* mZ 1930-2300,0330
04001 7 MHZ 2200-0100
11 MH2 1200-1300
1930-1900
0*30-0700
19 MHZ 1900-2100
2030-2200
3 mz 2330-0130
0200-0230
0300-0930
9 mz 2330-0000
ii mi oooo-oo30
3 mZ 2130-2200
2230-2300,0230
-0700S 4 HHI 2200
-2300,2330-0000,
0400-0330,0*00
0*301 3 mz 2130
23001 * mz 0*00
-0630,2230-2300
7 mZ 0130-0200
0330-0400,0900
0*00,0900-09301
9 mi 1030-2230
3 mz 023O-0300
0330-0430,1(30
11001 * MHZ 1930
21001 11 MHZ 1330
1*001 19 MHZ 1(00
-1930,2200-2230
Table 3e.
SFI E.UR0RE
9 mi 0100-0 130
09 33-C»00
» mZ 0*30-0700
9 mZ 0003-0200
1930-190C
11 MHZ 13OC-1330
2130-2200.0300
-09301 19 mz
1230-1300,1430
1300,1*00-1630
2200-2230
SCRITH AMERICA
9 MHZ 1100-1130
ASIA
2200-2230,2300
0100,0130-0230
0300-0330
1130-1330
3 mi 1130-1200
0300-0330
3 mZ 1000-1030
1200-1230,2200
-2230; 7 MHZ 1900
19001 0300-0330;
9 mz 1300-1330
1900-1730,2000
-2100.2130-2230
2330-0200.0300
-03301 11 MHZ 1200
-1300.1630-1900
2200-2230.2330
00301 19 MHZ 2300
-0230;
17 MHZ 1430-1600
3 MHZ 1200-1230
* MHZ 0930-0630
7 mz 0600-0630
11 mZ 0930-0630
0330-043(
13 mi 0200-0230
0300-0630
AFRICA
NORTH AMERICA
11 MHZ 1630-1700
1(00-2000.2030
21001 13 mz 1200
1300.1330-1600.173O
1900,1900-22001
17 MHZ 1200-1230.
1400-1530
3 mZ 2130-2200 11
2230-2300.0430 19
0600; 4 MHZ 2200
2300.0400-0430
0300-0330; 3 MHZ
2130-2300:
6 MHZ 0600-0630
7 mZ 2330-0000.0330
7 mZ 2330-0000
04 30,0900-0630
0(00-0930: 9 MHZ K3C
-2200.0230-0300.
0300-0330;
11 NH2 1300-1330.1930
-20301 IS MHZ 1900
-1630.1730-1(00
7000-2200! 17 mi
1200-1230. 1400-1900
* mZ 230O-2330
3 MHZ 0330-0400
2 mz 2200-2230
2
MHI
1030-
1100
3 mz 2330-0000
) mz 04)0-0990
•000-0130,3230
3 MHZ 090C-0930
9 mz 1030-1100
1200-1230
0300-0430.0930
1130-1200
-0300: 7 mz Z230
* MHZ 0430-0900
* MHZ 0900-0930
7
MHI
0390-0690
-06)01 -MHZ 2200
9 mz 0200-0290
-2 300,0100-0200
1100-11230
1030-11001 7 mz
9
MHI
1100-1230
-2300.2330-0000
* mz 0490-0900
0*00-0(001
11 mZ 2)00-02^0
1130-1230. 1930
11
KHZ
0*00
-0630
0300 -0430. 06 00
* mz 1200- i4oo
9 mz 040O-04S0
2000: 9 mz 1100-
Ii
ml
0100
-0*30
5 mZ 2030-2200
09)0-04)0
11 MHZ 2300-2330
1130.1200-1230
0600-0630; 6 MHZ
0))0-04)0
0030-01301 is mz
143O-1S30. 1*30
2230-0000;
ii mz oooo-OMo
1430-1430.1900
-1730.1(00-2100
7 mz 0900-0330,
03OO-0SS0.05OO-
-1*90.1700-1730
2200-0990: 11 mz
0600-0630.0730
0990;
1900-1930
1030-1300.1330
-0(00,0300-0330.
19 mz 0090-0100
17 mz 1930-1*00
-1400.1700-2030
2IOO-2200.2230-
2300,2330-0000
19 MHZ 1030-1100
1430-1330,2330
0390.1900-1930
17 MHZ 1200-1230
0400-0430; * mz
1(30-2230. 2330
0000,0200-0400
11 MHZ 2030-2100
2130-22301 19 mi
1900-1 700. 1(00
1(90,1*00-1290:
17 MHZ 1330-1400.
-1(00.0100-01301
21 MHZ 1300-1350
20)0-2200
1790
3 mz M3O-OTO0
9 MHZ 0630-0700
4 WZ 1100-1130
3
mi
1000-1130
3 mz 2200-0100
9 mz 0190-0200
* mz 01M-02M
0900-1030.1130
1200-12301 9 mz
4
MHI
1230-1)00
0330-0(00:
0900-04901
(3 3O-04O0.0T00
1130- 12001 4 mz
1100-1190,1900
3
MHZ
0(00-1200
4 mZ 1930-2030
« mZ 0*30-0900
HMl t mz
1130-12(9)
19301 » mi 2200
T
MHZ
0*00-1100:
2100-0 100,03)0
* mz 1130-1200
02 30-0930
1Z30- 1300 .0OO0
22901 T mz 1030
*
PWI
0>)0-0(30
0730: 9 mz 2190
1990-2000
* mZ 2130-2230
0200.09 90-0430
1230,1930-2000
1
m
0400
-0430
0000,0900-09901
9 mi 1400-14)0
00 00-0013.0100
3 MHZ 0200-0230
2100-2900.0330
1!
mi
2300
-00)0
6 mZ 2100-2 900
2OOO-2O3O.2330
0130: ii mz
4 MHZ 0030-0200
04(01 4 mz 1100
3)00-0990.0600
0400-0*001 7 MHZ
OO00I
1T30-KO0.03M
i no- 1700
1130. 1(0 0-1(30
0*301
0930-0900;
2100-23301
04301 12 mz 1300
io mz 0*00-1010
ZOOO-Z990.0Z30
* mz 1(90-0000
1330.2030-21001
11 mZ 2300-0230
0900: 11 MHZ 1030
0900-09)0: ii mz
Table 3f.
D2 - 81
SFI EUROPE
15 HHZ 1330- 1400
1600-1630,2030
21 MHZ 1500-1630
7* 5 HHZ 0100-1130
6 MHZ 2300-2330
0000-0030,0130
-0200,0230-3300
04 30-0500;
9 MHZ 2130-2230
0100-0400 11 HHZ
01 00-04O0, 17C0
2030-2100
12 HHZ 1200-1230
15 HHZ 1300-1330
73 5 MHZ 0130-0230
6 MHZ 3000-0030
0700-0730.0800
OB 15; 7 HHZ 0730
0800; 9 HHZ 1500
1530; 11 MHZ 1700
1600; 15 HHZ 1230
1330,1630-1630
1700-1800
72 5 HHZ 2130-2200
0100-0130
6 HHZ 2300-2 330
0100-0130
0300-0330
7 HHZ 0100-0200
9 HHZ 2030-2130
2230-2330,0000
00 30,0100-0200
0300-0330
11 HHZ 1630-1730
1930-2000,0130
0300; 15 HHZ 1330
1400,160-0-1730
1730-1830
SOUTH AMERICA
15 HHZ 2100-2130
000-0200
ASIA o
1230,1600-1630
1800-1830,2100
2130,2200-2230
15 HHZ 1900-1930
0000-0300,1100-1200
3 HHZ 013
4 HHZ 233
0100-0230
-1130;
0130,0230
6 HHZ 09
9 HHZ 003
0130-0200
0400,2300
11 MHZ
0-0300
0-0030
• HOC
HHZ 0100
-O3O0
00-0930
0-0100
0300
2330
00-0230
3 HHZ 063 0-0700
4 HHZ 2330-0000
0400-0430,0930
-1000; 5 HHZ 0400
0630-0700,1000
1030; 6 HHZ 1000
-1100: 9 MHZ 0400
0500,2000-2100
15 HHZ 1900-1930
2100-2133,0000
0200
2 HHZ 1030-1100
3 HHZ 0000-0100
0130-0200,0700
0830,0900-0930
4 MHZ 2 330-0000
0030-0100,0200
0230,0400-0430
0500-05 30,1000-
1030; 5 MHZ 0200
0230: 6 MHZ 0700
0730, 1000-1030
9 HHZ 0000-0200
10 HHZ 2300-2330
11 HHZ 2100-2130
2300-2330,0030
3 MHZ 1130-1200
2300-0000
4 MHZ 1130-1200
2230-2300,0100
-0200; 5HHZ 1100
1130,1300-1330
6 MHZ 1000-1200
7 MHZ 2100-2300
9 MHZ 1230-1330
2230-2330.0230
-0300
1400;
0500,1200-1330
1630-1800,2100
2200,2300-2330
12 MHZ 1300-1330
1400-1430,1800
1800-1930,0100
-0130
21 HHZ 1400-1530
4 HHZ 1130-1230
6 HHZ 1130-1330
0030-0100
7 HHZ 1100-1330
9 HHZ 1130-1200
1300-1400,1900
£030; II MHZ 1100
1230,1500-1530
1800-1830,0130
0200; 12 MHZ 1230
1300: 15 MHZ 1100
-1130,12 00-1300,
1400-1500,1600
1700,1800-1830
2300-04000
17 MHZ 1430-1600
2 HHZ 2130-2200
4 HHZ 1030-1100
5 HHZ 1130-1230
2330-0000
9 HHZ 1100-1130
1700-1730,1930
2030,2100-2130
2200-2230
11 HHZ 1000-1030
1100-1500,1930
2030,2100-2230
12 KHZ 1200-1300
II HHZ 1200-1300
17 HHZ 0200-0300
2 HHZ 0900-0930
3 KHZ 1000-1030
1130-1200
4 HHZO9OO-1330
6 HHZ 1000-1300
7 HHZ 0730-0800
9 MHZ 1500-1530
11 HHZ 1100-1200
1930-2000; 15 HHZ
2030-2100,2300
10 MHZ 1300 0030,0230-0630
I HHZ 0430
5 HHZ 0730-0900
0630-0900
1300-1330
9 MHZ 1200-1230
11 MHZ 2230-2330
0600,0630-0700
3 MHZ 1030-1200
4HHZ 0800-0900
1130-1200
7 MHZ 0600-0800
1000-1100
9 HHZ 0700-0730
1130-1200.1500
1600; 11 HHZ 0200
0230,0600-0730
15 HHZ 1630-1900
0130-0500
AFRICA
1930-2130; 15 MHZ
0800-1500,1530
1600,1800-1830
2130-2300
3 MHZ 2130-0000
03 30-0430
4 HHZ 2030-0000
4 HHZ 2030-0000
0230-0700; 5 HHZ
2130-2230,0500
-0600; 6 MHZ 2130
2330,0330-0400
7 HHZ 2130-2330
9 HHZ 1630-1700
1800-2130,0300
0330: 11 HHZ 1430
1500,1730-2200
0600-0630
15 HHZ 1300-2300
3 HHZ 2230-0000
0300-0400
4 MHZ 1100-1130
2100-0000,0300
0400-0500,0600
-0700; 5HHZ 0400
11 HHZ 1230-1400
6 MHZ 2130-2200:
6 HHZ 2130-2200
7 HHZ 0600-0700
9 HHZ 1900-1930
11 MHZ 1OCO-1O30
1530-1800,1830
2030,2130-2200
15 HHZ 153O-1T0O
00 00-0 100
1800-1900
3 HHZ 2230-0000
0230-0400;
4 MHZ 2100-0000
0300-0500,0630
0700; 5 HHZ 2200
0000,0530-0700
6 HHZ 1930-2230
0000-0030,0 00
0330,0600-0630
7 HHZ 2300-2330
06 30-0730
9 MHZ 1230-1400
1800-2100,2200
22 30,2300-2330
0230-0300 11 MHZ
NORTH AMERICA
0000-0100
3 MHZ 0100-0300
4 MHZ 2 3 31 -01 M
0300-0330,0430
-0500,0630-0730
6 MHZ 0030-0100
9 HHZ 1130-1400
0400-0430
11 HHZ 0630-0700
1200-1230;
15 HHZ 2000-2030
4 HHZ 0030-0530
0630-0700
5 HHZ 0430-0600
6 HHZ 0600-0630
1000-1030
1930-2100
0100-0130
3 HHZ 2330-0000
0030-0100,0200
0230; 4 MHZ 2130
2200,0030-0500
5 HHZ 0330-0530
6 MHZ 1100-1200
0200-0230
9 HHZ 2130-2200
0130-0200,0330
0400,0430-0500
11 MHZ 0300-0330
15 HHZ 2000-2100
2200-0000
Table 3g
SFI EUROPE
SOUTH AMERICA
AFRICA
NORTH AHERICA
71 6 HHZ 2300-2330
0430-0500,0800
0830;
7 MHZ 0300-0330
9 HHZ 2300-0100
0130-0200
11 HHZ 0100-0300
70 7 HHZ 2130-2200
9 MHZ 2100-2130
15 HHZ 1400-1430
1700-1730
2 HHZ 013 0-0200
3 HHZ 1100-1200
3 HHZ 0400-0430
4 HHZ 1100-1200
1000-1030,2300
5 HHZ 1100-1200
2300-2333;
2230-2300
4 MHZ 0 33 0-0430
6 MHZ 2230-2300
0500-0530
7 HHZ 0930-1000
6 HHZ05 30-0600
1030-1130; 9 HHZ
11 MHZ 0200-0230
0800-0830,0900
15 HHZ 1300-1330
0930,1930-2100
1400- 1430
11 HHZ 1130-1200
2200-2300
1330-1400,1730
1930,2000-2030
2100-2200,2330
-0000.0400-0430
15 MHZ 1600-1700
2030-2100,0230
0300,0400-0430
4 HHZ 0400-0430
3 HHZ 1230-1300
15 HHZ 2200-2230
4 MHZ 1130-1200
5 HHZ 12 30-1300
7 HHZ 1130-1230
9 HHZ 1330-1400
11 MHZ 1830-1930
2100-2200,2330
-0000;
15 HHZ 1900-1930
3 HHZ 1030-1130
4 HHZ 1030-1130
6 HHZ 0800-0830
9 MHZ 0600-0630
1130-1230
11 HHZ 0230-0300
0330-0400,0600
0630; 15 HHZ 0200
-0230,0500-0530
3 HHZ 1100-1130
6 MHZ 0830-1030
9 HHZ 1100-1300
69 7 HHZ 0100-0130
0200-0230
9 MHZ 2300-2330
0000-0230
11 HHZ 2300-2330
0100-0230
15 HHZ 1700-1800
2100-2130,2200
-2300,0200-0^:"
4 HHZ 0000-0030
0400-0430
9 MHZ 0000-0300
0430-0500
11 HHZ 0000-0030
6 HHZ 1100-1230
2230-2330
7 MHZ 1200-1300
2100-2130,2300
2330,0400-0430
9 HHZ 1030-1100
1800-1830,1930
2200; 11 HHZ 1000
-1030,1100-1200
1230-1300,1730
-0030; 12 HHZ 0200
-0230; 13 HHZ 0000
-0200,1100-1130,
1700-20000
17 HHZ 0230-0330
46 7 HHZ 0030-4100 4 HHZ 1000-1030 3 MHZ 0000-0030 4 MHZ 0630-0900
3 MHZ 1000-1030
4 MHZ 0800-0630
1000-1033
5 HHZ 0730-0930
5 HHZ 1030-1130
7 MHZ 0300-0530
1030-1100
9 MHZ 1230-1300
0430-0500
11 HHZ 0130-0330
0500-0530
15 HHZ 0300-0330
1600-1700,1630
2200; 15 MHZ 1230
-1330,1630-2030
2130-22001
21 HHZ 1600-1630
3 HHZ 2100-2200 3 HHZ 0230-0300
2230-0000,0230
03 30,0400-0530
4 HHZ 0400-0700
5 HHZ 0530-0700
6 HHZ 2200-2230
0330-0430; 7 HHZ
02 30-0300,0530
0700; 9 MHZ 0600
-0630; 11 MHZ 1300
1330,1730-2200
15 MHZ 1400-1700
1800-2100,2130
-2200
17 MHZ 1500-1700
3 HHZ 2300-0000
3 HHZ 1000-1030
0400-0530 4MHZ
6 HHZ 1100-1130
2100-2300,2330
9 HHZ 1130-1330
-03001 5 HHZ 0530
1600-1800,1630
-0630,1930-2230
1900,0300-0330
6 HHZ 2230-2330
11 HHZ 2300-2330
0300-0330,0500
15 HHZ 2000-2100
0500-0600: 7 HHZ
0000-0030,0430
06 30; 9 HHZ 0230-0300
11 KHZ 1930-2000.
2030-2100; 15 HHZ
1700-1630
2300-0030
3 HHZ 2230-2300
3 HHZ 0430-0330
03 30-0400,0430
5 MHZ 0530-0600
-0500,0630-0730
6 HHZ 0000-0030
4 HHZ 2200-2330
9 MHZ 1230-1300
0330-0630
11 HHZ 2200-2230
5 HHZ 2200-2330
0130-0230
0730-0930
13 HHZ 1330-1400
7 HHZ 2130-2200
1930-2130
0330-0430; 9 MHZ
1630-1900,1930
2030,2200-2230
0230,2200-2230
2030,2200-2230
11 HHZ 130O-1830
1930-2230,0030
01001 15 HHZ 1100-
1200,1330-1600,1730
1830,1900-2000,2300
2330,0130-0200
03 30-0600
3 HHZ 2330-0000
3 HHZ 04O0-O430
Table 3h.
D2 - 82
EUROPE
SOUTH AMERICA
ASIA
OCEANIA
AFRICA
NORTH AMERICA
0704-0730
11 MHZ 2300-C000
4 MHZ 1330-1400
7 MHZ 0730-0800
0330-0400; 4 MHZ
5 MHZ 0530-0600
9 ml 2200-0030
15 MHZ 2200-2230
0000-0030; 9 MHZ
9 MHZ 0600-0630
2200-2230,0230
11 MHZ 1200-1300
CI 30-0230
2300-2330
1930-2030,2100
08000830
04 00,0600-0630
0100-0130:
11 MHZ 22G0-0CK.0
2130,2200-2230
11 MHZ 0130-0200
6 MHZ 2100-2130
15 MHZ 2000-2130
OO30-03OO
11 MHZ 1300-1330
03 30-0400
03 30-0400
15 MHZ 2000-2130
15 mhzi'OO-1430
1700-1930,2000
15 MHZ 0200-0230
7 MHZ 0030-0130
0400-0430
2300-2330
2030,2130-2300
0000-0030,0100
0330: 15 MHZ 2230
0000-0130;
17 MHZ 1500-1530
0300-0330
9 MHZ 1630-2030
9 MHZ 1630-2030
2200-2230; 11 MHZ
06 30-0700;
15 MHZ 1800-1900
2030-2100; 17 MHZ
1330-1400,1530-1600
6 MHZ C13O-02O0
* MHZ 0330-500
4 MHZ 1030-1100
3 MHZ 0630-0730
3 MHZ 2330-0000
3 MHZ 0130-0200
9 MHZ 0000-0U30
0900-0930
6 MHZ 1100-1200
0900-1030
0430-0530,0600
4 MHZ 0300-0430
01 30-0200
5 MHZ 0330-0500
2200-2230
4 MHZ 0700-1130
4 MHZ 2030-2100
0500-0530,1000-1030
11 MHZ 1930-2100
0630-0730
9 MHZ 1930-2230
5 MHZ 0600-0630
2130-2230,0400
6 MHZ 0530-0600
0130-0200
11 MHZ 2300-2330
11 MHZ 1330-1400
9 MHZ 0430-0500
-0730; 5 MHZ 2230
1030-1100
15 MHZ 2100-2130
15 MHZ 1200-1230
1700-2000,2100
1200-1300
2300,0430-0630
1030-1100
2300-0000
2200.0000-0030
11 MHZ 0330-0430
6 MHZ 2130-2230
9 MHZ 0700-0730
15 MHZ 0000-0130
0630-0700
0300-0330,0530
11 MHZ 1130-1200
0330-0400,1600
15 MHZ 0230-0300
-0600: 7 MHZ 0300
1300-1330,1500
1630,1930-1900
0330-0400
0400,0430-0530
-1530,0030-0100
1700-1730
9 MHZ 1630-2030
11 MHZ 1500-1700
1900-2000,0400
-0430,0530-0600
15 MHZ 2030-2300
17 MHZ 1230-1300
0300-03 30,0530-0600
14 MHZ 2200-2300
15 MHZ 0130-0200
0300-0330
5 MHZ 013C-0230
3 MHZ 0 83 0-0900
« MHZ 0900-0930
* MHZ 0830-0900
3 MHZ 0300-0330
15 MHZ 2000-2100
6 MHZ 0200-0230
4 MHZ 0300-0400
1000-1030,2030
11 MHZ 0300-0500
4 MHZ 2200-2230
17 MHZ 1500-1530
11 MHZ 2100-2330
2200; 11 MHZ 1200
-1230,1600-1630
1700-1930,2100
2130,2300-0000
15 MHZ 2 100-2130
0130-0200
02 30-0300;
6 MHZ 2100-2130
7 MHZ 0400-0430
0600-0630
11 MHZ 0200-0230
0700-0730.1900
-1930,2330-0000
15 MHZ 2330-0030
02CO-0230
Table 3i.
On 6 July 1976 the flux was 67. The chart indicates many openings,
including: 4 MHz, Africa, 0400-0730 GMT; 4 MHz, Oceania, 0700-1 1 30 GMT. The
following was actually heard: Liberia on 4 . 770 MHz at 0635-071 1 ; Ghana on
4.890 and 4.915 MHz at 0602-0700; Papua New Guinea on 4.890 MHz at 0705-0720;
Australia on 4.920 MHz at 0700.
On 22 and 23 February and 7 March 1977 the flux was 78. Among the open-
ings on the chart are: 3 MHz, North America, 0330-0430; 6 MHz, Europe, 0330-
0400; 11 MHz, Africa, 1630-1 700, 1800-2000; 15 MHz, Asia, 2200-2230, 2300-0100.
These stations were heard with good reception: Guatemala on 3-300 MHz at 0340,
Portugal on 6.025 at 0335, Malagasy Republic (Radio Nederland) on 11.730 at
1930, Liberia on 11.940 at 1657, and Japan at 2300, 0000, 0100 all on 15.105
MHz.
On 7 June 1977 the flux was 89. Among the openings predicted by the chart
are: 9 MHz, Asia, 1830-1930; 11 MHz, Asia, 2100-2130; 15 MHz, Asia, 0400-0530.
The following stations were heard with good reception: India on 9-525 MHz at
1850, Pakistan on 11.625 MHz at 2115-2125, and Japan on 15-310 MHz at 0458.
On 28 December 1977 the flux was 102 and the following openings were pos-
sible: 4 MHz, Africa, 2130-2300, 0400-0430, 0530-0630; 4 MHz, Oceania, 1000-
1400; 9 MHz, Africa, 2030-2100; 4 MHz, Asia, 1300-1330; 12 MHz, Asia, 1800-
1830. These stations were heard on that day: Liberia on 4.770 MHz at 2140,
South Africa on 4.880 MHz at 0417, Papua New Guinea on 4.890 MHz at 1026-1400,
Ghana on 4.915 MHz at 2200-2300, 0600-0615, Australia on 4.920 MHz at 1215-
1234, Nigeria on 4.932 MHz at 0605, Malaysia on 4.950 MHz at 1329, Nigeria on
4.990 MHz at 2109 and 0558, Uganda on 9-730 MHz at 2031, Kuwait on 12.085 MHz
at 1802.
D2 - 83
On 27 February 1978 the flux was \kO. The chart predicted: 3 MHz, North
America, 1100-1200, 0230-0300; 4 MHz, Asia, 1030-1230; 4 MHz, Oceania, 1 1 30-
1200; 15 MHz, Asia, 1200-1230. The following stations were heard: Guatemala
on 3-300 MHz at 1117-1130, 3-330 MHz at 0200-0300, and 3380 MHz at 1130;
Mongolia on 4.763 MHz at 1 030-1 045; Sumatra on 4.768 MHz at 1135; Papua New
Guinea on 4.890 MHz at 1139; Cambodia on 4.908 MHz at 1111; Vietnam on 15.012
MHz at 1201 .
On 29 April 1978 the flux was 1 83 - The chart shows 6 MHz, South America,
1000-1100; 9 MHz, Asia, 2200-2230; 3 MHz, Oceania, 1030-1 1 30 ; 9 MHz, Africa,
2030-2100. The following were actually heard that day: Papua New Guinea on
3-335 MHz at 1059-HOl and Peru on 6.020 MHz at 1016-1033.
7. CONCLUSION
Thus a method to predict solar radiation levels and thereby radio wave
propagation predictions has been developed for North America. With additional
help and data, charts could be compiled for every part of the globe.
ACKNOWLEDGMENTS
I would like to thank my parents , Isaac and Rachel, for
their patience and understanding with my work; my brother , Marct
for reveiwing much of the work and for his useful suggestions .
A special thanks to Andrew Blumberg , Dov Banner , Michele
Kitchner for their ideas and support , and to Morris Kitchner
for his help and use of his dissertation . Thanks to all who
have reveiwed this paper for their many and useful corrections .
Last but not least thanks to G-d above who has guided me along
this strange path.
REFERENCES
Dixon, Wilfred J., and Frank J. Massey ( 1 969) : Introduction to Statistical
Analys i s .
King, J. W., and W. S. Newman ( 1 967) : Solar Terrestrial Physics.
Kitchner, Morris (1955): Some Non-Parametric Tests for Time Series. Master
of Arts dissertation, Department of Economics, Mew York University.
"Radio Propagation Forecast Information Via Radio Station WWV", U.S. Depart-
ment of Commerce, institute for Telecommunications.
Seber, G.A.F. (1977): Linear Regression Analysis.
Snodgrass, Joan G. (1977): The Numbers Game.
Solar Geophysical Data, explanation of data reports, U.S. Department of
Commerce, National Oceanic and Atmospheric Administration.
Wonnacott, Thomas H., and Ronald J. Wonnacott (1977): Introductory Statistics
for Business and Economics.
D2 - 84
GRAFEX PREDICTIONS
J. F. Turner
Ionospheric Prediction Service
Australian Department of Science and the Environment
P.O. Box 702
Darlinghurst NSW 2010, Australia
A form of presentation of HF radio propagation predictions is
described. This form contains the information needed for opera-
tional and short term planning, is compact and can be produced
rapidly using a lineprinter.
1. INTRODUCTION
The Australian Ionospheric Prediction Service produces two types of pre-
dictions each intended to meet a specific need. The first type is intended
for operational purposes which are mainly concerned with the selection of
frequencies. The second type is for planning and design and
involves calculation of quantities such as path loss. For convenience these
are referred to as frequency and path predictions respectively. The availabil-
ity of the world maps of basic ionospheric parameters in numerical form has
made it possible to produce both type predictions using an electronic compu-
ter. Frequency type point-to-point predictions can be produced quickly and in
large quantities. Although the path type predictions can also be produced
reasonably quickly, they involve much more computing time. The bulk of com-
munication prediction requirements are for operational purposes which can be
satisfied by the frequency type predictions.
As the computing involved in producing a frequency type prediction can
be performed very rapidly, there was a need for a way to display the results
which was correspondingly rapid. The GRAFEX form was developed to meet this
need. In addition to being fast the prediction computations produced a con-
siderable amount of detail and the GRAFEX form attempts to show as much of
this information as considered desirable in a reasonably compact form. (The
name GRAFEX has no special significance; it was the name of the computer pro-
gram which produced this form.)
2. FREQUENCY TYPE PREDICTIONS
The frequency type prediction information considered useful includes the
upper decile, median and lower decile F-layer MUFs, the E-layer median MUF and
the ALF for each hour (UT) for the first two possible modes. The MUF depends
on the ionization density and height of a layer and an obliquity factor.
D2 - 85
The F2 layer, because of its greater height and density and its persis-
tence, is the most important layer for long-distance communication. However,
because the angle of incidence of a signal on the lower layers is greater, the
obliquity factor is greater for these layers and under certain conditions the
MUF for a lower layer may be greater than that for the F2 layer. Consequently,
in making predictions, the lower layers must be taken into account.
A signal propagated by the ionosphere may travel by one or more reflec-
tions from the ionized layer. If only one ionospheric reflection occurs this
is referred to as single hop or more correctly as a IF or IE mode depending
on the layer involved. There is a limit to the range at which a signal can be
received by one ionospheric reflection. For the F layers this limit is between
3,000 and ^,000 kilometers and for the E layer it is about 2,000 kilometers.
It should be noted that the Fl and F2 layers are treated together. The ALF is
an estimate of the lowest usable frequency and is derived empirically from a
combination of absorption and the E-layer cut-off.
Signals may travel between two terminals by more than one mode. Of course,
the minimum number of reflections will use longer hops and have larger obli-
quity factors than the others. Thus the highest frequency which can be used is
usually the MUF for the simplest mode. For higher modes the obliquity factor
for the ALF will decrease and thus the lower limit of the range of usable fre-
quencies will apparently decrease. However, ot^er actors such as the loss of
signal at each reflection, shielding by lower layers and poor aerial directiv-
ity, will tend to offset the lowering of the minimum by this decrease in the
obliquity factor. Generally only the first two possible modes need to be con-
sidered .
3. PRESENTATION OF PREDICTION INFORMATION
The information could be displayed in tabular form but this is not easy
to use; a diagram is preferable. Figure 1 shows the predictions in tabular
form with appropriate headings. This form is only used for special purposes.
A graph with time of day as the horizontal axis and frequency as the vertical
axis showing the change in the various parameters through the day is a useful
form. However, producing graphs either manually or using a computer plotter
is slow and defeats the objective of having the output match the speed of the
prediction computation. The GRAFEX form overcomes this by converting the pre-
dictions to a form which can be printed by the fast line printer but retains
the diagramatic appearance.
By examining the numerical predictions for any desired hour it is possible,
for a specific frequency', not only to determine whether the frequency will be
received or not, but also to make some estimate of the probable quality of the
received signal from the prediction information about the various modes.
It has been found that the information in the predictions applied to a speci-
fic hour and frequency can be fitted into one of eleven categories.
D2 - 86
tone
SVDttv
BRlbBANE
LENCTH
731 WIS
AZIMUTHS
14.5
193.
5 DATE
MARCH
00
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
FIRST
MODE
u»
151
155
156
156
15*
153
151
148
146
129
1 16
110
110
113
1 10
108
102
92
87
85
97
124
137
144
HEP
137
1*0
1*2
141
139
137
136
133
128
111
100
95
91
89
87
85
83
77
73
71
83
112
124
131
1.0
118
122
<23
122
120
119
118
113
110
95
85
81
75
72
70
68
66
62
59
38
70
97
107
113
£«UF
121
126
129
127
123
115
103
86
63
30
0
0
0
0
0
0
0
0
0
22
62
86
102
113
ALF
49
30
51
50
49
-.6
42
35
18
0
0
0
0
0
0
0
0
0
0
0
25
38
43
*7
SECOND
NOt»E
uo
117
121
122
122
121
120
118
115
1 14
104
9!
90
90
93
91
88
83
75
72
69
75
92
103
111
m6d
106
110
111
111
110
108
106
104
101
91
83
79
75
74
73
71
68
64
61
59
66
■84
?3
101
LD
93
96
97
97
96
94
92
90
87
77
71
68
63
60
59
3 7
55
51
48
47
56
73
83
88
tn^
67
70
71
71
68
64
57
48
3?
16
0
0
0
0
0
0
0
0
0
12
34
47
36
82
ALF
36
37
37
37
36
34
31
26
15
U
0
0
0
C
0
0
0
0
0
0
19
28
32
35
UNIT 100KHZ
tumt
DARUIN
BRISBANE
LENGTH
2846 KMS
AZIMUTHS
129.2
301 .
5 OATE
MARCH 100
0
1
2
3
4
5
6
7
8
9
10
1 1
12
13
14
15
16
17
18
19
20
21
22
23
FIRST
MODE
UO
3*5
366
375
375
379
381
3o7
379
350
325
291
275
268
275
286
275
268
250
223
197
202
254
298
316
MEO
3U9
328
336
336
339
342
343
336
310
278
240
227
221
217
214
206
201
187
165
146
149
207
267
283
LP
273
293
308
308
311
309
307
301
276
239
202
191
185
176
17 1
164
160
144
123
109
111
169
235
250
EMUF
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ALF
137
142
K5
K5
143
138
130
1 16
9/
81
0
0
0
U
0
0
0
0
0
0
0
86
114
128
SEiONO
MODE
uD
220
239
240
236
241
239
243
234
232
206
161
171
173
17 1
179
176
ITj
162
146
126
120
139
189
219
MEl>
202
216
216
213
217
213
217
209
200
172
151
143
139
137
137
135
134
123
11 1
103
98
120
174
199
Lf.
175
192
199
196
198
192
196
189
175
147
129
124
1 16
1 12
113
1 10
107
96
87
82
78
100
150
173
EMOF
ISO
191
179
198
193
183
168
144
1 1 1
61
U
J
0
0
U
0
0
0
0
0
0
96
133
160
ALF
85
8b
90
90
89
87
82
75
64
0
0
0
a
0
0
0
0
0
0
J
38
61
74
81
UNIT 100KHZ
Figure 1 . Tables showing UD, median and LD F layer MUFs,
E-layer MUF and ALF for two modes for two circuits.
Figure 1. Tables showing UD, median and LD F layer MUFs,
E-layer MUF and ALF for two modes for two circuits
k. GRAFEX SYMBOLS
These categories for the frequency (with the symbols) are as follows
1. ( ) above all the normal MUF. (Of course the signal
may be propagated by an unusual mode (e.g., sporadic E)
or abnormally high ionization density.) This symbol is
also used when the frequency is below the lowest ALF.
2. ( . ) below the first F mode upper decile MUF but above
the median MUF. The frequency will be propagated on
more than three days of the month but less than half
the days.
3. (%) below the first F mode median MUF but above the
lower decile MUF. The frequency will be propagated on
more than half the days in the month but less than 90% of
the days.
A. (F) below the first F mode lower decile MUF but above
either MUF's. Communication on frequencies in this cate-
gory should be usable on almost all days except, possibly,
when an ionospheric storm is in progress.
5. (E) below the first E mode median MUF but above the first
F mode median MUF. (The variation throughout the month
about the E median MUF is very small so deciles are not
quoted for this layer.) Propagation may still be possible
by the F layer on a few days of the month.
6. (P) below the first E mode MUF and below the first F
mode median MUF but above the F mode lower decile MUF.
Propagation by first E mode is possible on all days and
by the first F mode on more than half the days.
D2 - 87
7- (B) below the first E mode MUF and below the first F mode
lower decile MUF. Propagation is possible by both E and
F modes on most days of the month.
8. (M) below the first F mode lower decile, below the second
F mode median MUF and maybe also below the first E MUF.
The mode by which the signal will be propagated in prac-
tice will depend on several factors including the aerial
elevation angle and beamwidth used.
9. (S) below the second F mode median MUF and below the first
mode ALF.
10. (A) very close to an ALF. (If the ALF is the first mode
ALF the mixed mode symbol (M) overrides this.)
11. (X) below the second E mode MUF. Other modes such as
mixed E and F and higher order F modes are also probable.
(Categories 2-7 must be above the first mode ALF and 8, 9 and 11 must be
above the second mode ALF.)
5. COMMENTS ON THE SYMBOLS
In most cases these eleven categories are adequate to describe the propa-
gation conditions but occasionally some unusual combination of numerical
values will produce a peculiar classification. Some changes and additions to
the categories have been made since the GRAFEX process was first used. These
were introduced because it was found that the earlier categories were inade-
quate in enough cases to justify the increased complexity of additional sym-
bols.
It should be noted that the second F mode upper decile and lower decile
MUFs are ignored. The categories 8 and 9 use the median MUF. It is con-
sidered that including the extra categories using the second mode deciles
would unduly complicate the resulting picture without much advantage. However,
there is one very important case involving the second mode deciles. This is
when no first mode F layer communication is possible. This can occur on cir-
cuits with hops between 3000 and *t000 kilometers length. If the F layer
height is low the maximum length of the hop may be less than that required.
In this case the highest frequencies that can be used are controlled by the
second mode and Categories 2 and 3 are determined from the second mode deciles
(Categories h to 8 are not possible).
6. FORMAT FOR PRINTING GRAFEX PREDICTIONS
The basic GRAFEX process involves determining, for a given frequency,
the category for each hour using the numerical predictions, the appropriate
symbol being printed in a tabulation (the 0 hour symbol is repeated for the
2Ath hour). The frequency is printed at the left hand end of the line.
The lines of GRAFEX symbols can be arranged in various ways but there
are two forms commonly used.
If a user only requires predictions for specific frequencies a GRAFEX
line can be produced for each of the frequencies. These can be printed with
circuit name and date to give a very compact and complete prediction (Figure
2).
D2 - 88
**KEY**
USABLE LESS THAN 507. OF DAYS
7. USABLE LESS THAN 907. OF DAYS
F FIRST F LAYER MODE ONLY
E E LAYER PROPAGATION POSSIBLE
P PROPN E (90%) OR F (50-90%) DAYS
B BOTH E&F MODES POSS. 907. OF DAYS
M MIXED FIRST AND SECOND F MODES
S SECOND F MODE BUT NO FIRST MODE
A HIGH ABSORPTION
X COMPLEX MODES
SYDNEY BRISBANE MARCH ICO
FREQ 00 02 04 06 OS 10 12 14 16 IS 20 22 24
MHZ .............
15.0
12.5 I??? 7. 7. % 7. 7. . . 7. 7.
10.0 M M M M M M M M M 7. 7. B M M
7.5 M M M M M M M M M M M M M 7. 7. 7. 7. 7. . . 7. M M M M
6.0 XXXXXXMMMMMMMMMMMMM7. MMMXX
4.0 AAAAAXXXMMMMMMMMMMMMMXXAA
00 02 04 06 08 10 12 14 16 IS 20 22 24
DARWIN BRISBANE MARCH 100
FREQ 00 02 04 06 OS 10 12 14 16 IS 20 22 24
™" ^•••••. .......
24.0 F F F F F F F F F 7. . 7. F F
20.0 M M M M M M M M M F F 7. 7. 7. 7. 7. 7. . . . 7. F F M
16.0 X X X X X X X M M M F F F F F F 7. 7. 7. . . F M M X
12.0 X X X X X X X X M M M M M M M M M M F 7. 7. M X X X
S.O AXSMMMMMMMMMMMXX
6.0 XMMMMMMMMMMM
• ••••••......
00 02 04 06 OS 10 12 14 16 16 20 22 24
Figure 2. GRAFEX predictions for specific frequencies.
The second form (Figures 3 and k) is the one more frequently used. This
is the GRAFEX point-to-point circuit prediction. The GRAFEX lines are pro-
duced for a range of frequencies in fixed steps starting from the highest.
When the full set of lines has been printed the result is a diagram which
looks very like the graphical form but actually provides much more informa-
tion about the various modes. A table is printed on the right of the GRAFEX
diagram. This table lists the median hourly values of the F-MUF, EMUF and
ALF for the first then the second modes. A short key giving the meanings of
the symbols is printed under the GRAFEX diagram. Details of modes and
number of hops are included. There is a heading at the top of the diagram
giving the circuit name, the path length and the date to which the predic-
tions apply. A GRAFEX circuit prediction will fit on a standard kh page or
half a line-printer page.
D2 - 89
NAME
VERT
FRE8
MHZ
22.0
21.5
21
20,
20.
19
19,
18
18,
17
17
16
16,
15
15,
14,
14,
13,
13,
V.
12
11
11
10,
10,
9,
9,
SYDNEY BRISBANE
ANG. IN DEGREES
00 06 11
LEN6TH 731 KM
IF 34-40 2F 54-
18 24
DATE MARCH
59 1E12
UT FMUF EMUF
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
. .XX
XXXX
XXXX
XPPP
PBBB
bbbb
BMMM
MMMM
MMMM
MMMM
MMMM
MMMM
MMMM
MMMM
MMXX
xxxx
xxxx
xxxx
xxxx
xxxx
AAAA
7.7.7.
Y.Y.X
Y.Y.Y.
r>XX
BBF
MBF
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
XMM
XXM
XXX
XXX
XXX
AXX
AA
7.X.
XX.
Y.Y..
FXX
FFY.
MM 7.
MM 7.
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
XMM
XMM
XMM
AXM
X
X. .
XXX
Y.Y.Y.
MF7.
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
XX .
XXI
Y.Y.Y.
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
MMM
.XX
.7.7.
XXP
XXB
XBB
7. FBM
X BMM
.F MMM
.F MMM
. .8 MMM
. XM MMM
. XM MMM
XXM MMM
XMM MMX
XMM MXX
MMM XXX
MMM XXX
MMX XXX
MMX XAA
MMX AA
MXA
00 06 12 16 2
. USABLE LESS THAN 507. OF DAYS
X USABLE LESS THAN 907. OF DAYS
F FIRST F LAYER MODE ONLY
E E LAYER PROPAGATION POSSIBLE
P PROPN E (90Xl OR F (50-907.) DAYS
B BOTH E4F MODES POSS. 90X OF DAYS
M MIXED FIRST AND SECOND F MODES
S SECOND F MODE BUT NO FIRST MODE
A HIGH ABSORPTION
X COMPLEX MODES
00
01
02
03
04
05
06
07
06
09
10
1 1
12
15
16
17
IS
19
20
21
00
01
02
03
04
05
Oo
07
06
09
10
1 1
17
IS
19
20
13.7
14.0
14.2
14.1
13.9
13.7
13.6
13.3
9
8
8
8
8
7
7
7.1
8.5
11.2
12.4
13.1
13.7
10.6
11.0
11.1
11.1
11.0
10.6
10.6
10.4
10.1
9.1
S.3
7.9
7.5
7.4
7.3
7.1
6.6
6.4
6. I
5.9
6.6
8.4
9.5
10.1
10.6
12.1
12.6
12.9
12.7
12.3
11.5
10.3
6.6
6 . 3
3.0
10.
11.
3.5
1 .6
3.4
4.7
5.6
Figure 3- GRAFEX circuit predic-
tion for a short path
length with IE mode
possible.
100
2E25
ALF
4.9
5.0
5. 1
5.0
4.9
4.6
4.2
3
1.
0
5
8
0
0.0
0.0
0.0
2.5
3.8
4.3
4.7
4.9
0.0
0.0
3.5
3.6
NAME
VERT.
FREff
mh:
40.
39.
38.
37.
36.
35.
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
28.0
27.0
26.0
31.
30.
29.
25.
24.
.0
.0
23.0
22 . 0
21.0
20.0
19.0
18.0
17.0
16.0
15.0
14. 0
13.0
12.0
11.0
10.0
o.O
£.0
7.0
o.O
5.0
*.0
3.0
2.0
DARWIN BRISBANE LENGTH 2846 KM
ANG. IN DEGREES IF 04-06 2F 18-
00 06 12 16 24
.XXX
.7.7.7.
7.XFF
XFFF
XFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FMMM
MMMM
MXXX
MXXX
XXXX
XXXX
XXXX
xxxx
xxxx
xxxx
xxxx
xxxx
AAAA
XX
XXX
XXX
FX7.
FFF
FFF
FFF
FFF
FFF
FFF
FFF
FFF
FFF
MMM
MMM
XMM
XXM
XXM
XXX
XXX
XXX
XXX
XXX
XXX
XXX
AAX
FX.
F7. .
FX.
FF7.
FCX
FFX
FFX
FFF
FFF
FFF
MMF
MMF
MMF
MMM
MMM
MMM
XMM
XMM
XMM
XXM
XXM
XXM
AXS
XS
X.
XXX
00
06
XXX
xxx
FXX
FFX 7.7.7.
FFF XXX
FFF FFX
FFF FFF
MFF FFF
MMF FFF
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
MMM MMM
12
X . . . . X
XX. ..X
XX. ..X
XXX ,.F
FXX ..F
FFX XXF
MFX XXF
MMF XXM
MMM XFM
MMM MFM
MMM MMX
MM" MMX
MMM MMX
MMM MM
MMM MM
MMM MM
MMM MM
MMM MM
IS
.XX
.XF
XXF
XXF
XFF
FFF
FFF
FFF
FFM
FMM
FMM
MMX
MMX
MXX
MXX
XXX
XXX
XXX
XXX
XXA
USABLE LESS THAN SOX OF DAYS
USABlE LESS THAN 90X OF DAYS
FIRST F ^AYER MODE ONLY
MIXED FIRST AND SECOND F MODES
SECOND F MODE BUT NO FIRST MODE
HIGH ABSORPTION
COMPLEX MODES
DATE MARCh
21 1E 0
UT FMUF EMUF
DO
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
13
19
20
21
OC
0!
02
03
04
05
Od
07
06
09
10
1 I
30.9
32.8
33.6
33 . 6
33.9
34.2
34.3
33.6
31.0
27.8
24.0
22.7
22.1
28 .3
30.9
21 .6
21.3
21.7
20.9
20. C
ir.2
15. 1
Is. 3
13.7
13. 7
19
10
3
20
9
8
21
12
0
^i
17
4
23
19
9
2-.
10
i
1S.0
19. 1
19.9
19.8
9.3
6.3
o. 1
1.0
Figure k. GRAFEX circuit predic-
tion for a path longer
than the maximum IE
mode.
100
2E 4
ALF
14.2
14
14.5
14.3
13.8
13.0
11. o
9.2
8,
0,
0,
0,
1
0
0
0
0.0
0.0
0.
0.
0.
0.
0.
0.
S.i
11.4
12. S
13.7
6.5
8.6
9.0
9.0
e.=
o.c
0.0
C . G
8. USING GRAFEX PREDICTIONS
There are a number of ways communicators can use their frequencies. For
example, the broadcaster will want to be sure that the broadcasts are on fre-
quencies which can be received in the target area, while the radio amateur
may wish to use frequencies above the median MUF on days when the MUFs are
higher than normal. The GRAFEX predictions contain information to meet the
needs of both these communicators. It is not possible to set down rules for
using GRAFEX predictions which will completely meet the needs of all users
but is is possible to set down a few general comments.
Use of a frequency during the hours when the GRAFEX symbol is 'F' should
ensure that good communication is achieved most days of the month except when
an ionospheric disturbance occurs.
Using a frequency when the symbol is '%' should be satisfactory on more
than half the days of the month. In this case the operator should have a back
up lower frequency available for those periods when the selected frequency is
not propagated. A situation requiring the use of a frequency in the '%'
region can arise around local nighttime when the MUF is falling rapidly and
especially just after dawn when the frequencies are rising sharply.
It is not considered desirable to try to use frequencies when the symbol
D2 - 90
is '.' except for special purposes.
It should be possible to maintain good communication during times when
two modes are possible ('M1 and 'B') provided that the signals by the two
modes are not (almost) equal in strength. Generally signals by the first E
mode ('B') and the second F mode ('M') are several dBs weaker than the signal
by the first F mode. If the aerial favors the first F mode this will further
reduce the possibility of interference. In some cases the aerial may favor
the second F mode particularly on the lower frequencies. The vertical angle
information printed below the circuit name and date may be helpful in resolv-
ing the problem.
Operation with frequencies at times when they are in the 'X' region is
not considered desirable as there are likely to be several modes available at
least one of which will interfere with the wanted mode.
It is not considered desirable to operate close to the ALF. The symbol
'A1 indicates that the frequency is much too close to the ALF. However, even
when the frequency is outside the 'A1 region it may still be unsatisfactory.
It is known that the absorption varies from day to day. Also there is often
a small amount of sporadic E layer which may increase the E layer cut off
frequency. These factors are not currently allowed for in IPS predictions.
9. CONCLUSION
The GRAFEX form of presentation of point-to-point frequency test predic-
tions has evolved over several years of use and assessment of its usefulness.
It has proved to be a far superior method of presenting such predictions than
the earlier graphical methods or tabulations such as shown in Figure 1.
D2 - 91
'
3. ABSORPTION, FIELD STRENGTH AND RADIO NOISE PREDICTIONS
PREDICTION OF RADIO WAVE ABSORPTION IN THE IONOSPHERE
J.O. OYINLOYE
Department of Physics
Un i versi ty of I lor in
I lor in , Nigeria
A new empirical formula of the form L = F(U,x,l) has been found
for predicting at a fixed frequency of 2.2 MHz both the temporal and
spatial variations of radio wave absorption L in the ionosphere where
U, x and I represent the ionizing flux, the solar zenith angle and
the magnetic dip angle respectively. The new formula removes the
necessity for having different absorption laws for the long-term
(solar cycle) and short-term (diurnal and seasonal) temporal
variations. It also incorporates latitude variation through the
factor !•
INTRODUCTION
The variation with wave-frequency of radio wave absorption in the
ionosphere, obtained at vertical incidence, has been treated in detail by
GEORGE (1971) and SAMUEL and BRADLEY (1975). Once the absorption at one
frequency (e.g. 2.2 MHz) is known, it is a straightforward matter to obtain
the absorption at any other desired wave frequency. GEORGE and BRADLEY (197^)
have also shown how to convert absorption observed at vertical incidence to
equivalent absorption at oblique incidence.
The purpose of this paper is to obtain an equation of the form
L = F(U,x,I) (l)
that will predict 2.2 MHz absorption L at a given intensity level of the
ionizing flux U, a given solar zenith angle x and at a given location having
a magnetic dip I . Essential departures from the absorption laws hitherto
used are (a) the introduction of U dependence into the diurnal and seasonal
variations and (b) the explicit introduction of x into the long-term variation
such as the solar cycle variation. It has been inferred from the time
variations in the 1-8A° solar X-ray flux measured by SATELLITE SOLRAD 9 -
EXPLORER 37 that the ionizing flux could vary significantly during the course
of a day, from day to day and from month to month and that these variations
are usually accompanied by similar variations in observed radio-wave absorp-
tion (GNANALINGAM, 1974; OYINLOYE, 1978a). This observation shows that the
influence of U on the time variation in absorption cannot be neglected even
when considering the diurnal and seasonal variations. It has in fact been
D3 - 1
shown by OYTNLOYE (1978a) that by considering the factor U, the "equatorial
seasonal anomaly" in absorption that has posed a problem for about two decades
can be explained.
The experimental data required for the prediction work are the flux data
U and the absorption data. It has been found from an earlier work by the
author (OYINLOYE, 1978a) that time variations in the 1-8A solar X-ray is
adequately representative of time variations in effective U at a large range
of heights in the ionosphere. Also in the present work, time variations in
the intensity of 1-8A° solar X-ray measured by SATELLITE SOLRAD 9 - EXPLORER
37 have been used to represent the time variations in the effective U. The
hourly values for 19b9-1970 are taken from the 'Solar Geophysical Data, Part I1
published by ESSA Research Laboratories.
Experimental data on absorption have been obtained from absorption
bulletins issued by Colombo, Freiburg and Ibadan and also from "Absorption
Data for the IGY/IGC and IQSY" issued by the World Data Centre A. Where there
were no observed values at 2.2 MHz, absorption at this wave frequency has been
deduced by the method described by GEORGE (1971) and SAMUEL and BRADLEY (T975K
Information on the relevant stations is given in Table 1.
Table 1 INFORMATION ON STATIONS
Station
Geog.Lat.
(deg.)
Geog.Long.
(deg.)
Dip angle
(deg.)
Year of Absorption
Data Used
Ahmedabad
23. ON
32. 2E
32N
1958
Bangui
4.6N
18. 6E
13S
1958, 1959
Colombo
6.9N
79. 9E
5S
1957-1959, I9b4-1970
Freiburg
48. ON
7.8E
b4N
1958, 1959, 19b4-l966, 1969
Ibadan
7.4N
3.9E
6S
1957, 1958, 1966-I9b8
Singapore
1.3N
103. 8E
17S
19b4
Tokyo
35. 7N
139. 5E
49N
1958, 1959, I9b4-1965
Tromso
69. 7N
18. 9E
78N
1957, 1958
PREDICTION FORMULA
The prediction formula of equation (l) can be written in the separable
form
L = r(l)V(U,x)
where r(l) is the latitude factor and \p (U,x) is the time variation at a
reference station where r(l) is unity. In this paper, Colombo is adopted as
the reference station because several years of absorption dataare available at
this station. Once"y(U,x) is obtained for Colombo, it is an easy matter to
D3
C 0 L 0 M BO 1969-1970
i-yo-i
1-90-
x = 30°, MORNING
1*85-
1-80-
175-
1-70-
.' ,.''
g* 1-65-
• • _•*■* • •
_ i
• • ^* • • • • •
• ^^ • •• •
1-60-
• s^> •
1-55-
•
1-50-
1 1 1 T
-0-8
1-95-,
1-90-
-0-4
T 1 1 1 1 1 1 1 1 1
0-0 0-4 Log u0-8 1-2 1-8 2-0
Log U
Fig. li DETERMINATION OF THE RELATIONSHIP BETWEEN 2.2 MHz ABSORPTION (dB)
AND 1-8A° SOLAR FLUX (MILLIERG CM"2 SEC-1) FOR x=30° AT COLOMBO
D3 - 3
co co co
II I
"*\£«
£ z *~
ill
• * < *^* M
* • \"« 4
R V- '
O LU ->
• M 4
iO \
» K 4
1 ^i
« *
8 \
o>
O
CD
2
o
_J
o
o
o
o
i
o
i
CO
o
(0
o
o
C7>
-«* O
6 -»
I
1 6o"|
co to to
.1 ? i
1
1
o
CM
O
X
oo
(/)
o
O
o
1
o
_»
00
o
6
o
_J
LL
O
CO
LU
1 Bcq
1 6oi
Fig. 2: DETERMINATION OF THE RELATIONSHIP BETWEEN 2.2 MHz ABSORPTION (dB)
AND COS x FOR 0.80£U^1.20 (MILLIERG CM-2 SEC-1) AT COLOMBO
D3
predict absorption for any other station using appropriate value of r(l) for
that station.
o
Variation At Colombo At A Fixed Zenith Angle x=30
2.2 MHz absorption data at Colombo for x=30 were obtained from the
diurnal plots on regular 'world days during the period 1969-1970- From a plot
of Log L against corresponding Log U shown as Fig. 1, it is found that the
relationships between 2.2 MHz absorption L and 1-8A solar X-ray U for x=30
are the following:
L = 48.0U(0-l4^°-005) Morning (2a)
L = 5u5Ui0'lk^°'005) Afternoon (2b)
Though GNANALINGAM (1974) has suggested that at a fixed value of x, L is
linearly related to ftf , it has been found by the author (OYINLOYE, 1978b)
that the L-JU relationship is only approximate for a short range in the
values of U, For a large range of values of U, the L— /U plot is not linear.
Variation At Colombo At A Constant Level of U
Figure 2 shows the cos x dependence of 2.2 MHz absorption at Colombo at a
constant intensity level of U given by 0.80 ^U£1.20. From the plots the
relationships between L and cos x are as follows:
L = 55«3(cos x) — For the monthly noon values (3a)
L = 55.l(cos x)°-96±0.01 For 0730-1130 hours (3b)
L = 57.6(cos x)0*7 -0,02 For 123O-I630 hours (3c)
It is seen from equations (3a) and (3b) that within the limit of experimental
errors, both the seasonal and morning hourly variations in L have the same
cos x dependence once the influence of U is removed. That the afternoon cos x
dependence of equation (3c) is different from (3a) and (3b) points to the
reality of the existence of the asymmetry in the diurnal variation of L,
Within the limits of experimental errors equations (3a), (3b) and (3c) tend
to the same limit as the zenith angle x approaches zero. Because equation
(3b) is derived from a wider spread in x values and a greater number of data
points than equation (3a), a combination of equations (3b) and (3c) will be
used in preference to a combination of equatiohs (3a) and (3c) as input for
the explicit determination of equation (l).
"Nf (U,x) at Colombo
The combined influence of U and x on the time variations of 2.2 MHz
absorption at Colombo can be put in the form:
T T ,.O.l43 m ,, ,
L = L U cos x (4)
o
where L is the value of 2.2 MHz absorption at Colombo when U = 1.00 millierg
cm " sec " and x = 0.0. Substituting equations (2) and (3) into (4) gives
55.1 U0,143 (cos x)0,96 Morning (5a)
57.6 U0,143 (cos x)°-78 Afternoon (5b)
Of course, within the limit of experimental errors, both equations (5a) and
(5b) tend to the same value as x approaches zero. Equations (5a) and (5b)
represent the time variations at Colombo given by"Vi>(U,x).
D3 - 5
Latitude Variation, r(l)
Absorption at any other station besides Colombo can be obtained by-
multiplying equation (4) by the factor r(l) to give the full equation of the
type
L = r(l)L U°#l43cosmx (6)
o
where for a given zenith angle x, r('l) is the ratio of the 2.2 MHz absorption
at a given station having dip angle I to that at Colombo and m takes the
values O.96 and O.78 for the morning and afternoon hours respectively. The
magnitudes of L for the morning and afternoon hours are given respectively
by equations (5a) and (5b).
Figure 3 shows the latitude variation of r(l) with the dip angle I and
this also constitutes the normalized latitude variation of noon absorption at
2.2 MHz. The stations from which were obtained the data used in Fig. 3 are
listed in Table 1. The IGY and IQSY are regarded as high and low sunspot
periods at all the stations except at Ibadan where 1966 data were used for
the low sunspot period and 1967-1968 data for the high sunspot period. 1958
Ibadan data are subsequently used for validating the prediction formula of
equation (6). It is to be noted from Fig. 3 that at low latitudes r(l)
appears to be independent of the solar cycle while beyond about magnetic dip
angle 1=30 ? r(l) seems higher during low sunspot period than during high
sunspot period. The error in r(l) is largest during winter at stations under
the influence of the "winter anomaly in absorption".
VALIDATION OF PREDICTION FORMULA
In this section the prediction formula of equation (6) is first tested
for the reference station of Colombo where r(l) is unity and then subse-
quently for other stations.
Figure 4 illustrates the good fit of observed data to the predicted
calculated curves for short-term temporal variations at Colombo. Figures
4(a), 4(b) and 4(c) illustrate respectively the diurnal variations for the
regular world days in 1969 and 1970 for the equinoctial month of April , the
solsticial month of January and all the months of the year. The appropriate
values of U for the diurnal variation in January are shown as Fig. 4(aii).
For Figs. 4(b), 4(c) and 4(d) the observed time variations are for a con-
stant level of U given by 0.oO£U£1.20 millierg cm-2 sec-1. The vertical
dashed lines in Figs. 4(a) and 4(b) indicate the times of minimum x. The
time lag between the occurrence of minimum x and maximum absorption has been
considerably discussed in another paper (OYINLOYE, 1978b). The diurnal
variation shown in Fig. 4(c) covers a large range of x and the dashed line in
this diagram is used to illustrate the continuity of equations (5a) and (5b)
as x approaches zero.
Figure 4(d) shows the good fit of the observed seasonal variation to
the predicted curve. The similarity in the seasonal variations of
absorption and cos x is also noteworthy.
Figure 5 further illustrates that on a long term basis the observed
data at Colombo have a good fit to the predicted variation of absorption with
Sa which is the observed 10.7cm solar flux adjusted to 1 A.U. and measured
in 10-22 vy-2 hz-1# From a plot of log U against log Sa, it has been
D3 - 6
rH -, SUMMER
N
X
2 1'2n
(N
1-0-
< -
£0-8-
I-
V
High sun spot
Low sun spot
A
i
1^.
L
r-
1
i ..-*
CL
o1^l EQUINOX
GO
<
LL
O
1-2-1
y
1-0- .I
7
o
<:
>
S2-0H
3
< 1-8-
Q
LU 1.5-
t 1-4-J
or
o
Z 1-2-
1-0-
\
N
-i
0-8
1
WINTER
fl.
I I
I
a
1/
*t—
4 //
A
10
1
20
30
40 50 60
70
80
MAGNETIC
DIP ANGLE I DEGREES
D3 - 7
S
5
M
H
O
CO
1
CM
d,
O
2
O *
a H
H H
< 2
H 3
5
a
> 2
M
H W
H 2
S3
q8
S
mS
O <
2 >
en
•H
9P'i
1-03S3-WD 6j8E_0lfn
Fig. 4: A COMPARISON OF PREDICTED AND OBSERVED SHORT-TERM TEMPORAL
VARIATIONS OF 2.2 MHz ABSORPTION AT COLOMBO
D3 - 8
COLOMBO
80n
70
60
50 H
L1
X = 30°, MORNING
(a
SO-i
70-
60-
X= 30°, AFTERNOON
(b)
L1
60 80 100 120 HO 160 180 200 220
10?Cm SOLAR FLUX, SallO^Wn^Hz-1)
Fig. 5: A COMPARISON OF PREDICTED AND OBSERVED LONG-TERM TEMPORAL
VARIATIONS OF 2.2 MHz ADSORPTION FOR x=30° AT COLOMBO
D3 - 9
z
<
Q
<
CD
Q
LU
>
cc
LU
(/)
CO
O
cm
Q
LU
>
LU
(/)
CD
O
CM
8
<7>
10
8
ap ' i
Fig. 6: A COMPARISON OF PREDICTED AND OBSERVED SEASONAL AND LONG-TERM
TEMPORAL VARIATIONS AT IBADAN. ERROR BARS INDICATE THE
QUARTILES ABOUT THE MEDIANS
D3 - 10
*-— PREDICTED
] OBSERVED
L.M-T
CO
10 ~1 — i — i — i — i — i — i — i — i — i — i — i — i
06 08 10 12 14 16 18
5
z
o
8
H
1
c/)
S I
S S
CM W
• O
N W
Q
°?
yj w
ga
h ca
5S
>£
< o
z tt
3 U
Q
i
w
pa
o
U
o §
H 5
DS Q
U3 Z
*S
X ^
in
I— I
g
tx.
O
z
o
en
9
&
3 H
--» <
<s) O
w M
Q
U Z
Z H
n
81
< M
ffi
a
D3 - 11
50-i
40-
30-
20--
m 10
1966
FREIBURG
\
OBSERVED
VALUE
COMPUTED
VALUE
1 — | — i — I — I — : — i — r
t — I
5<H 1969
1 — i — i — i — i — i — i — i — | — i — i
J FMAMJ JASOND
Fig. 8:
found that
A COMPARISON OF PREDICTED AND OBSERVED SEASONAL VARIATIONS
OF 2.2 MHz ABSORPTION AT FREIBURG FOR BOTH LOW AND HIGH
SUNSPOT CONDITIONS. ERROR BARS INDICATE THE QUARTILES ABOUT THE
MEDIANS
.. _ (5.34+0.19) -26.11
U = S — e
a
(7)
L values for the continuous lino in Fig. 5 have been calculated from
equations (5a) and (5b) setting :;=30° and substituting for U in equation
(7)» LI and L2 for the broken lines correspond respectively to the upper
and lower limits of U given by equation (7)«
The predicted formula is also tested for Ibadan and Freiburg data.
Ibadan and Freiburg are regarded as typical equatorial and non-equatorial
D3 - 12
stations respectively. Furthermore, Freiburg is under the influence of
the "winter anomaly" in absorption while Ibadan is not. For the purpose of
comparison with observed absorption appropriate values of r(l) have been
used in computing the predicted absorption. All the computed variations
of absorption in Figs. 6, 7 and 8 except that for 1969 at Freiburg have
been based on appropriate medians of the 10.7cm adjusted solar flux S . The
curves shown as LI and L2 in Fig. 8 give a measure of the uncertainty
in calculated L arising from the uncertainty in the conversion equation
(7) for U. The predicted 1969 variation of absorption at Freiburg is
based on direct 1-8A solar X-ray data.
From Figs. 6, 7 and 8 a good agreement is evident between observed
and predicted long-term seasonal and diurnal variations at Ibadan and
seasonal variations at Freiburg during low and high sunspot conditions.
It is also worth mentioning that a good agreement has been obtained for
the predicted and observed diurnal variations at Tokyo for the years
1958-1959? averaged over each season. Diurnal data were not available for
such a comparison at Freiburg.
CONCLUSION
A prediction formula for 2.2 MHz absorption has been obtained and
tested. For prediction purposes at a given station, the parameters
required are the 1-8A° solar flux (or where not available the adjusted
10.7 solar flux), the normalized latitude factor r(l) and the zenith
angle x. The present work further emphasizes one of the needs for X-ray
monitoring for the purpose of short-term prediction in particular.
REFERENCES
Geroge, P. L. (1971): The global morphology of the quantity J NV.dh in
the D- and E-regions of the ionosphere. J.atmos. terr.Phys. ,
33: 1893
George, P. L. , and P. A. Bradley (1974): A new method of predicting the
ionospheric absorption of high frequency waves at oblique incidence.
Telecomm. Journal , 4-1 : 307
Gnanalingam, S. (1974): Equatorial ionospheric absorption during half a
solar cycle (1964-1970). J.atmos. terr.Phys. , 36: 1335
Oyinloye, J.O. (1978a): On the seasonal variation of absorption of radio
waves in the equatorial ionosphere. J . atmos . terr ♦ Phy s . , 40: 793
Oyinloye, J. 0. ( 1978b): A new form of representation for temporal and
spatial variations in radio wave absorption in the ionosphere. Accepted
by J. atmos. terr.Phys.
Samuel, J. C. , and P. A. Bradley (1975)* A new form of representation of the
diurnal and solar-cycle variations of ionospheric absorption.
J. atmos. terr.Phys. , 37: 131*
D3 - 13
ON THE SHORT-TERM PREDICTION OF THE SPACE-TIME
DISTRIBUTION OF AURORAL ABSORPTION
R. A. Zevakina, M. V. Kiseleva
Institute of Terrestrial Magnetism
Ionosphere and Radio Wave Propagation
of the USSR Academy of Sciences
Moscow, USSR
Instead of qualitative, short-term predictions of the absorption
for the zone as a whole (Zevakina, 1975), we propose a method of
quantitative prediction in decibels, taking account of the latitu-
dinal and diurnal variation of absorption.
As the magnetic activity grows, absorption in the auroral zone increases
and the zone itself widens. Driatskii (197*0 and Hargreaves (1965) present
empirical relations of the absorption on the magnetic activity (K and A H) .
However, these relations cannot take into account the large fluctuations of
absorption values.
We have investigated the correlation of absorption with the auroral
indices of magnetic activity - AE, K-indices and variations of the horizontal
component (A H) of the geomagnetic field at auroral stations. Moreover, we
have studied the variation of the statistical and latitudinal distributions
of the auroral absorption for different levels of magnetic activity. The
autocorrelation analysis of absorption has been carried out and, on the basis
of autocorrelation and relation to the magnetic activity, a numerical method
of prediction has been developed. Test cases are presented which demonstrate
the accuracy of the method.
To this aim, we have used the tables of hourly values from riometric
recordings made at four stations located at different latitudes: Heiss Isl.
(corrected geomagnetic latitude, 73-8°N), Dikson (67.2°N), Murmansk (64.0°N),
and Kiruna (64. 3°N) -during the years of high (1968) and low ( 1 964) solar
activity. We have also used the charts of auroral absorption during 1964,
1965 and I969 (World Data Center A, 1970- The absorption was measured at a
frequency of 32 MHz at Heiss and Dikson Isls. and in Murmansk and at a
frequency of 27 MHz in Kiruna.
The statistical distribution of auroral absorption has been examined for
a quiet geomagnetic field (K = 0 - 2), and for weakly (K = 3 ~ 4) , moderately
(K = 5 _ 6) and strongly (K > 6) disturbed states of the geomagnetic field,
separately for the daytime (6-12 hrs LT) and nighttime (22-04 hrs LT) hours.
D3 - 14
For each station, its own K-indices were used.
of absorption were omitted from the analysis.
Periods with polar-cap type
Figure 1. Probability (P, %) of
different values of the auroral
absorption (L, dB) at various
levels of magnetic activity for
Heiss (a) and Dikson (b) . solid
curve - day; dashed curve -
night.
Figure 1 illustrates the statis-
tical distribution of auroral absorp-
tion during 1 968 from the data obtained
on the Heiss and Dikson Islands. From
figure 1 it follows that the character
of the statistical distribution of
absorption is about the same in the
daytime and nighttime hours.
As the magnetic activity increases,
the distribution changes at all sta-
tions, but more considerably in the
middle of the absorption zone. On
Heiss Isl., absorption is predominantly
low. In 1968, it did not exceed 0.3 dB
for 85% of the time during quiet and
weakly disturbed conditions, 75% of the
time during moderate conditions and 55%
of the time during strongly disturbed
conditions. Absorption equal to and
over 1 dB was observed on the Heiss
Isl. only 2% of the time during weak
disturbances, 3% during moderate and
11% during strong disturbances.
In the middle of the zone (i.e. at
Dikson Island) high absorption (> 1 dB)
was registered much more often,
especially during moderate and strong
disturbances. On Dikson Isl., it was
observed k% of the time during quiet
conditions, 13% of the time of weakly
disturbed conditions, 19% under moderate and 27% under strong disturbances.
At the other auroral stations, the maximum of the frequency of occurrence
during quiet and weakly disturbed conditions is observed at low absorption
values (at 0.3 dB) , but under moderately and strongly disturbed conditions at
high absorption values (> 1 dB) . Over the solar activity cycle the absorption
distribution does not change significantly.
The latitudinal distribution of the frequency of occurrence of auroral
absorption exceeding 1 dB, has been considered by Driatskii (197*0- In order
to calculate the characteristics of radiowave propagation, apart from the
frequency of occurrence, one should know the variation of the absorption value
with latitude at different levels of the solar and magnetic activities.
In order to study the latitudinal absorption distribution, we have used
the charts of absorption during substorms in 1964, 1965 and 1969. which have
been compiled from the data of 36 stations situated on corrected geomagnetic
latitudes $ from ^k.k^H to 86°N. Because two maxima can be observed in the
diurnal dependence of auroral absorption, one in the pre-noon hours and the
D3 - 15
other at midnight, the latitudinal distribution has been determined for noon
and midnight values averaged over all substorm periods at the same magnetic
activity. Figure 2 shows such distributions over magnetically quiet
(Z Kp <_ 15), weakly disturbed (15 < £ K <_ 25) and also moderately and strong-
ly disturbed (Z K„ > 25) days during years of low and high solar activity.
Strongly disturbed days were few; accordingly, the distribution at IK > 25
mainly characterizes moderately disturbed conditions. From the figure it
follows that the latitudinal distribution varies with increasing magnetic
activity considerably more during the nighttime than it does in the daytime.
The zone width (absorption values > 0.5 dB) varied from 12° to 18°, due to
the displacement of its southern and northern boundaries. During 1 969 the
absorption was higher and the zone itself wider than during 1964-1965 only
at E Kp > 25. For Z Kp < 25, absorption during 1969 turned out to be lower
than during 1964-1965- This result is somewhat unexpected. Possibly, it is
associated with the limited amount of initial data or with a cyclic variation
of absorption whose maximum does not coincide with that of solar activity
(Zhulina, I969).
It should be noted that the spread of values from the average latitudina
distribution is rather large. The root-mean-squarei deviations (in dB) for
the various latitudes at different levels of magnetic activity during 1964-
1965 and 1969 are given in Table 1. It can be seen that the root-mean-square
deviations are largest in the middle of the zone (cf) = 62-69°) at a high
magnetic activity.
From the statistical and latitudinal distributions it is clear that the
absorption increases with increasing magnetic activity. In order to estimate
this dependence quantitatively, we have determined the correlation of the
absorption with K-indices during the same interval, during the preceding
interval, during the interval two intervals before and with hourly values
of the horizontal component of the geomagnetic field (A H) with the shift
from 0 to 6 hours.
Because the correlation may vary with the time of day, we considered the
correlation coefficients separately for the midnight (00 hr LT) , morning
(10 hrs) and evening (18 hrs) hours at each station. From the data obtained
at Dikson, Kiruna and Murmansk during 1 968 , these correlation coefficients
70 65 60 55* 75 70 65 60 55'4>
D3 - 16
Figure 2. Latitudinal dis-
tribution of auroral absorp-
tion at different levels of
magnetic activity during
1964-1965 (a) and I969 (b) .
Dashed curve for
15 < I Kp < 25,
sol id curve for
Z Kp < 15
and dash-dot curve for
Z K > 25.
P
Table 1. Root-Mean-Squared Deviations of
Absorption in dB.
Corrected
Geomagnet ic
Day
Night
Lati tude
ZK < 15
P-
15<ZK <25
ZK >25
P
ZK <15
P-
15<ZK <25
ZK >25
P
1964 -
1965
>70
0.75
1 .08
1.62
0.29
0.69
0.27
62-69
1.26
1.76
1.79
1 .22
1.76
0.27
55-61
0.40
1.30
0.15
0.27
1.06
0.18
55-75
1.05
1.54
1.39
1.00
1.48
0.22
1969
>70
0.00
0.51
1.19
0.00
0.18
0.50
62-69
0.95
1.61
2.73
0.23
1.16
2.49
55-61
0.50
0.34
0.38
1.15
1.25
1.78
55-75
0.10
1.22
2.07
0.14
1.02
2.02
are, on the average, the same at all three stations. During the nighttime
and morning hours, correlation coefficients are equal to 0.5 using K-indices
for the same interval, 0.6 for K-indices for the preceding interval and 0.4
with K-indices from two intervals before. During the evening hours, the
correlation coefficients turned out to be about 0.3 for all three intervals
of K-indices. Sometimes, they were nonrepresentat i ve or not statistically
significant. At equinox and in winter, the correlation coefficients were
somewhat higher than in summer, sometimes reaching 0.7- In summer, they were
sometimes nonrepresentati ve, which was also the case at the zone boundary.
The coefficients of correlation of absorption with hourly values of A H
have been found to be equal to 0.3_0.4 when A H was shifted by 2-6 hours;
they are somewhat lower when the values of A H during the same and nearest
hours are employed. The correlation of absorption with hourly values of A H
has turned out to be lower than with three-hour K-indices.
The correlation with both these indices indicates that absorption varies
with magnetic activity, but with a delay of 2-6 hours. A delay of the same
order has been found between the maxima of the diurnal dependences of mag-
netic activity and auroral absorption (Driatskii, 1966).
Since the coefficients of correlation of absorption with the indices of
magnetic activity are low and not always representative, the correlation
alone cannot serve as a basis for a quantitative prediction of absorption.
In order to estimate the possibility of extrapolating absorption from day to
day, taking into account the 27-day recurrence-tendency (the presence of
recurrence-tendency of absorption was shown graphically), we have determined
the autocorrelation coefficients for the mean midnight (during 22-02 hrs LT)
and mean noontime (during 10-14 hrs LT) absorption with the values of
absorption during the same hours on the previous day and also 2, 3» 26, 27,
and 28 days before the given day during 1964-1965 from the data of Kiruna
D3 " 17
and Murmansk and during 1 968 from the data of Dikson and Murmansk. The co-
efficients of autocorrelation do not change appreciably from month to month;
therefore, they are averaged over a year and are given in Table 2. From the
table it follows that the autocorrelation of the nocturnal absorption is •
slightly higher than that of the daytime absorption. The autocorrelation is
maximum with the absorption values for the previous day (0.59) and for 27
days before the given day (0.65). The autocorrelation coefficient for I968
is higher than for 196*1. Besides averaging over all days, the autocorrela-
tion coefficients was also determined for the disturbed periods only (Table 2).
These turned out to be usually higher than those averaged over all days.
Table 2.
Autocorrelation Coefficients
of Absorpt
.ion
•
Shift
in
Day
1968
Night
1964
Day
Night
Over di
da
sturbed
ys
time,
days
Day
Night
-1
0.47
0.59
0.55
0.51
0.64
0.58
-2
0.55
0.57
-0.02*
0.45
0.48
0.48
-26
0.41
0.50
0.51
0.10*
0.30
0.85
-27
0.63
0.58
0.55
0.65
0.57
0.63
-28
0.43
0.45
0.57
0 . 1 0*
*Nonrepresentat i ve coefficients.
From the above, it follows that the absorption autocorrelation coeffi-
cients are the largest with the values for one, two and 27 days before the
given day. Therefore, the extrapolation technique is applicable for the
prediction of absorption. This method is commonly used to predict magnetic
activity for a period of one to three days (Olson, I969) and fQF2, for a
period of several hours (Lyakhova, 1973)- The method makes it possible to
determine the predicted value as a function of the previous values:
A Lpr = a, A L, + a2 A L2 + a^ A L^,
where A L is a difference between the observed and median values of
L: A L = L , -L . . A L1t A L„ , A !_„-, are the values for the previous
obs, med . 1 2 27
days. To predict absorption one or two days ahead, we have determined the
coefficients a., a~ and a_7 by the least-square technique for all days and,
separately, only for disturbed conditions from the data obtained at Dikson
during I968 and at Kiruna during 1964-1965 (Table 3).
Making use of these coefficients, we have compiled forecasts of absorp-
tion for one or two days from the data of Dikson for 1 968 and of Kiruna for
1964. The accuracy of such absorption predictions was about 70% under
disturbed conditions and about 50% under magnetically quiet conditions.
The prediction of absorption for longer periods (to 27 days) can be made
on the basis of forecasts of magnetic activity, using the statistical and
D3 - 18
Table 3- Prediction Coefficients
Over al 1 days
Over disturbed days
Coef f i -
cient
1
Day
968
Night
1
Day
964
Night
Day
Night
al
0.44
0.36
0.36
0.48
0.38
0.46
a2
0.34
0.26
0.26
0.20
0.32
0.26
a„
0.08
0.29
0.35
0.24
0.52
0.37
latitudinal distributions of absorption for different levels of activity. In
this case, the value of absorption for the predicted level of magnetic
activity is found from the latitudinal distribution, and the probability of
this value at a given level of magnetic activity, from the statistical dis-
tribution. Forecasts made by this method for the Dikson Isl. for 1968 turned
out to be true in 85% of all cases in the days characterized by Z K < 15, in
95% for 15 < Z K < 25 when the absorption was estimated to within P50%.
P -
REFERENCES
Brown, R. B. and J. K. Barcus (1963): J. Geophys . Res., 68:4175-
Driatskii, V. M. (1974): The nature of abnormal absorption of the radio
emission from space to the lower high-latitude ionosphere. Leningrad.
G h i d rome teo i zda t .
Driatskii, V. M. (1966): Geomagnetism and aeronomy (Soviet), 6:1061.
Hargreaves, J. K. (1965): Planet. Space Sci . , 13:1171.
Lyakhova, L. N. and L. I. Kostina (1973): Geomagnetism and Aeronomy (Soviet),
13:59-
Olson, R. H. (1969): Solar Phys., 8:240.
World Data Center A (1971): Temporal development of geographical distribu-
tion of auroral absorption for 30 substorm events in each of IQSY (1964-
1965) and IASY (1969). Upper Atmosphere Geophysics, Report 16.
Zevakina, R. A., V. P. Kuleshova, E. V. Lavrova, and L. N. Lyakhova (1975):
Methods of short-term prediction of magnetic activity and the state of
the ionosphere. Instruction, Moscow, IZMIRAN.
Zhulina, E. M. (1969): In: Solar-terrestrial physics, iss. I., Moscow,
IZMIRAN, 177.
D3 - 19
DETERMINATION OF THE SOLAR CYCLE VARIATION OF
HF RADIO WAVE ABSORPTION AT LOW LATITUDE
K. M. Kotadia, A. Gupta and R. M. Kotak
Physics Department, Gujarat University
Ahmedabad 380 009, Gujarat, India
In this study, the prediction of ionospheric absorption measured by the
Al method at Ahmedabad (23°N, 72.6°E; magnetic dip 3*»°N) is based on the
solar activity represented either by the sunspot number or 10.7 cm solar
radio flux, which can be reliably predicted from their existing long series
of observations. Ahmedabad is a low latitude station situated at the well-
known fully developed F2-peak of the Appleton anomaly. It is shown here that
both the sunspot number and the 10.7 cm solar radio flux could serve on the
average as equally reliable indices for the long-term prediction of radio
wave absorption. Empirical formulae are established for the variation of
absorption with solar activity from the available data over a half sunspot
cycle. The constants involved in the linear relations are found to depend
on radio frequency, time of day and the season. With the availability of
data for one complete solar cycle, it would be possible to predict the
seasonal influence on the variation of radio wave absorption with solar
activity at fixed solar zenith angles, and the diurnal variation for each
month at different frequencies.
SUNSPOT NUMBER AND 10.7 cm SOLAR RADIO FLUX
The 12-monthly running averages of sunspot number Rz and 10.7 cm solar
radio flux Sjq 7 (measured at Ottawa, Canada and standardized to a distance
of 1 A.U.) are correlated for the 11-year period covering the years 1957~1968
from maximum to maximum of the solar cycle. A good linear fit is found
between these two indices and it is empirically expressed as
S]0>7 = 57-95 + 0.92 Rz (1)
with a correlation coefficient of 0.998. Thus the Sjg 7 flux remains at
about 60 units (1 unit = 10~22 W/m2/Hz) even at the solar minimum when Rz
is zero and the slope of the line is almost unity. However, the day-to-day
or instantaneous changes in the two quantities may not necessarily show so
good a correspondence as seen in their yearly averages. Recently, attempts
have been made to define a new index of solar activity in terms of the EUV
radiation flux observed in satellites for modelling of the neutral atmosphere
(Rawer et al . , 1978) .
D3 - 20
VARIATION OF IONOSPHERIC ABSORPTION WITH SOLAR ACTIVITY
Measurements of ionospheric absorption of HF radio waves were made for
nearly two solar cycles at mid-latitudes, particularly in Europe, and over
short periods at other places. One such series over a cycle exists at an
equatorial station, also, namely, Colombo in Ceylon (renamed as Sri Lanka).
The gap at low latitude was filled by starting the work of Al-method absorp-
tion on 1.8, 2.2 and 2.5 MHz at Ahmedabad (23°N, 72.6°E; I = 3k°U) in April
1972 with objectives of studying various aspects of the lower ionosphere. In
this paper, the prediction of ionospheric absorption as applied to communica-
tions is discussed.
From the data over a period of five years around the solar minimum when
Rz varied from about 100 to 10, it has been possible to establish empirical
relations showing how the ionospheric absorption changes with solar activity,
i.e. with Rz and Sjq 7. To remove the variation due to solar zenith angle
in finding the changes due to solar activity alone, the values of absorption,
L^b, at constant x are taken from the monthly median curves of its diurnal
variation. Here, the median values of L at cos x = 0-6 and cos x = 1 are
chosen, the former being the value available in all months at Ahmedabad and
the latter being taken from extrapolation of the linear graph of log L
against log (cos x) • Figure 1 shows the mass-plot of monthly median L at
cos x = 0-6 and cos x = 1 against the monthly mean Rz as well as Sjq 7 . A
line of the form y = a (1 + bx) obtained by the least squared error method
is drawn through the points. The scatter above and below the line does not
show deviations by more than 5 dB. Similar line-fits were obtained for
absorption on 1.8 and 2.2 MHz.
The linear graphs obtained in Figure 1 obey a formula of the form
L = a (1 + b Rz) dB, and (2)
L = a {1 + b (S1Q . -60)} dB. (3)
The empirical constants 'a1 and 'b' in the above formulae for absorption on
the three frequencies are given in Table 1 for cos x = 0.6 and Table 2 for
cos x = 1 •
Note from Table 2 that the value of 'a' decreases at higher frequencies,
but that of 'b' increases. In contrast, at cos x = 0.6, the values of 'a'
and 'b' both decrease at higher frequencies. However, the slope, i.e.
product 'ab' in the former case at cos x = 1 turns out to be nearly the same
within 10% for all the three frequencies, meaning that the rate of increase
in total absorption with solar activity is nearly the same although the
increase relative to the quiet-sun (solar minimum) value of absorption may
differ. The value of 'b' given in the tables is the mean for all months,
but it is found to change from month to month (Appleton and Piggott, 195^;
Schwentek, 1971; Patel et al., 1973). We shall also be able to find these
monthly values of 'b' on completion of our absorption measurements for one
full solar cycle and then test if the product 'ab' remains nearly constant
or not in all the months.
D3 - 21
AHMEDABAD
f= 2-5 MHz
20 40 60 80
Rz
C0S"X. = l-0
40
\^&ir-~
20
1 1
1 1 1 1 1 1
20 40 60 80
(% -60")
^ 10" 7 *
20 40 60 80
(S.0-7-6°)
o
o
1-7
— i — i i 1 —
v^OSX=l-0
1 ' — ' — «-
4S-.MI
.
1-5
-
-
^osx-o7^--^
jn = o-7|
-
1-3
-
1 1 1 1
1 , . ,
-
0-4
Figure 2
0-5
LOG Cf + fL)
06
Frequency dependence of
ionospheric total absorp-
tion at Rz = 0 for two
fixed solar zenith angles.
Figure 1. Variation of ionospheric absorption on 2.5 MHz
with sunspot number and 10.7 cm solar radio flux.
FREQUENCY AND COS x DEPENDENCE OF ABSORPTION
Absorption at Rz = 0 or Sjq -j = 60 seems to vary inversely as some
power of the effective frequency (f + f^) where f^ is the electron gyromag-
netic frequency. The exponent m in the inverse frequency variation of the
total absorption may change depending on the proximity of the observing wave
frequency to the E-layer critical frequency. This feature is clearly seen
from the different slopes of the two lines in Figure 2, which gives the plot
of log 'a' for cos x = 1 and cos X = 0-6 against log (f + f|_) where L is
longitudinal component of f equal to 1.12 MHz for Ahmedabad. The values of
'm' thus found are respectively 1.106 and 0.713, and the corresponding con-
stants of proportionality found by extrapolation of the above plots are 127
and 66. Values of m for other stations are given by Gnanalingam (1969)-
In prediction work for practical purposes, we are more interested in
total absorption. However, for scientific studies on the structural changes
in the D and E regions, one would attempt to separate the contributions of
these regions to Lhe total absorption and investigate in detail the depend-
ence of these contributions on time of the day, season, solar activity and
the operating frequency.
As regards the diurnal variation of absorption, it has been found that
the absorption varies as cosn X'
The mean value of n is found to remain
D3 - 22
Table I. Values of 'a' and 'b' for cos x = 0*6
Frequen
cy
Rz
S10
7
MHz
a,dB
22.22
b
a,dB
22.00
b
2.5
0.0033
0.0040
2.2
23-91
0.0036
23-35
0.0049
1.8
25.96
0.0045
23-97
0.0060
Table 2. Values of 'a' and ' b ' for cos X = 1 •
Frequen
cy
Rz
S10
•7
MHz
a,dB
31 .20
b
a,dB
30.60
b
2.5
0.0052
0.0067
2.2
33-77
0.005^
33.08
0.0069
1.8
39.66
0.0043
38.81
0.0058
within 0.75 and 0.80 depending on the operating frequency (Gupta and Kotadia,
1976). However, it changes from 0.5^ in winter to about 1.1 in summer during
the course of a year. Empirical formulae incorporating all these effects
have been given in different ways by different workers (Rawer, 1952; George,
1971 ; Lucas and Haydon, 1966; Samuel and Bradley, 1975)- We shall also be
able to fully evaluate them for a low latitude when our absorption data are
completed over one solar cycle, i.e. in 1 983 -
OBLIQUE INCIDENCE ABSORPTION AT CONSTANT x AND Rz = 100 EPOCH
The variation of vertical incidence absorption L explained above can be
applied to the case of oblique incidence absorption LQ^ for any angle of
incidence i at the entry of the wave into the ionosphere for one hop reflec-
tion in the absence of any scattering irregularities over a given distance
at appropriate frequency. Using the empirical relations derived for the
variation of L with solar activity, L0b can be calculated for different
paths, angle i being known from the height of reflection and the distance on
the earth of the intended communication circuit.
Suppose radio communication is desired over a distance of 1000 km by
way of one-hop reflection from the E-layer over a low latitude, as that of
Ahmedabad, under the following conditions: h = 100 km, i = 80° , sec i = 5«73,
fv = 2.5 MHz, fob = 14.3 MHz, Rz = 100 or S)0>7 = 150, and cos x = 0-6-
D3 - 23
Then from the values given in Tables 1 and 2 for a and b, and using Martyn's
Theorem, lQ^ works out to be 5-2 dB. In solar minimum condition, this
absorption comes down to 3-9 dB. However, at vertical incidence, the absorp-
tion on equivalent frequency 2.5 MHz comes down from 29. 1 1 dB at Rz = 1 00 to
22.22 dB at Rz = 0. In both the cases the absorption increases by a factor
of 1.33 from minimum epoch to Rz = 100 epoch of solar activity. But if we
consider in terms of dB difference, it is much smaller at the high frequency
used in actual communication over the surface distance of 1000 km. In the
similar manner, we can work out other examples of absorption on different
communication frequencies for the given operating conditions.
Superposed on the long-term regular variations of ionospheric absorption,
there are short-term changes also associated with events like solar flares,
PCA's, geomagnetic storms, Es and F-scatter irregularities and so on. It is
difficult to evolve a method for prediction of ionospheric propagation condi-
tions for such irregular changes. However, there have been attempts to
predict the occurrences of solar flares and geomagnetic storms about ^8 hours
in advance, and changes in their frequency and intensity of occurrences with
solar activity.
SUMMARY
In this paper, empirical relations are established to find the variation
of HF radio wave absorption in the lower ionosphere over a low latitude sta-
tion (23°N) with solar activity at two fixed solar zenith angles. The
prediction of absorption is based on the index of solar activity reliably
available from the solar astronomers. It is shown that the vertical inci-
dence ionospheric absorption at a constant solar zenith angle has a linear
relation with solar activity of the form L = a (1 + b Rz) , but the constants
involved in the empirical relation are functions of time of the day, season,
operating radio frequency and its proximity to the critical frequency of the
reflecting layer. An example is worked out to illustrate the method of pre-
dicting ionospheric absorption as applied to practical radio communication
which shows that the ionospheric absorption on the average at cos x = 0*6 f°r
a surface distance of 1000 km from the transmitter through one-hop reflection
in the E-layer over Ahmedabad at Rz = 100 would be 5-2 dB as against 3-9 dB
for Rz = 0 condition. This prediction does not take into account the month-
to-month seasonal changes in absorption and the additional effects due to
scattering irregularities and other transient events. We have planned to
continue the low-latitude ionospheric absorption measurements for one full
solar cycle in order to enable us to predict diurnal variation of absorption
for each month, seasonal variation at fixed solar zenith angles, dependence
of index n on cos x ar|d m for frequency-law on solar activity and other
related studies for establishing a complete generalized relation between
absorption and all factors affecting it. The normalized A-figure as studied
by Samuel and Bradley (1975) will also be studied for Ahmedabad then.
D3 - 2k
REFERENCES
Appleton, E. V., and W. R. Piggott (195*0 : Ionospheric absorption measure-
ments during a sunspot cycle. J. Atmosph. Terr. Phys., 5:1**1-
George, P. L. (1970- The global morphology of the quantity N dh in the D
and E regions of the ionosphere. J. Atmosph. Terr. Phys., 33 - 1 893 -
Gnanal ingam, S. (1969): Ionospheric absorption at low latitudes. 3rd
International Symp. 'Equatorial Aeronomy1, p-47 (PRL, Ahmedabad) .
Gupta, A., and K. M. Kotadia (1976): Ionospheric absorption on 2.5 MHz at
Ahmedabad. Ind. J. Rad. Space Phys., 5:211.
Lucas, D. L., and G. W. Haydon ( 1 966) : Predicting statistical performance
indexes for high frequency ionospheric telecommunications system.
ESSA Tech. Rpt. IER 1-ITSA 1 .
Patel , B. M., J. C. Patel , and K. M. Kotadia (1973): Winter anomaly in
ionospheric absorption of radio waves over half sunspot cycle. I nd . J
Rad. Space Phys. ,2:219-
Rawer, K. (1952): Calculation of sky-wave field-strength. Wireless Engr.,
29:287.
Rawer, K. , G. Emmenegger, and G. Schmidtke (1978): Some features of EUV
solar activity indices. XXI COSPAR Conf., W.G.IV, Paper A 2.6 at
Innsbruck (Austria) .
Samuel, J. C, and P. A. Bradley (1975): A new form of representation of
the diurnal and solar cycle variations of ionospheric absorption.
J. Atmosph. Terr. Phys., 37:131-
Schwentek, H. (1971): The sunspot cycle 1958-70 in ionospheric absorption
and stratospheric temperature. J. Atmosph. Terr. Phys., 33:1839-
D3 - 25
PREDICTION OF RIOMETER ABSORPTION FROM SOLAR
FLARE RADIO BURST CHARACTERISTICS
Pradip Bakshi
Physics Department
Boston Col lege
Chestnut Hill , MA 02167
and
Wi 1 1 iam R. Barron
Air Force Geophysics Laboratory
Hanscom AFB, MA 01731
Earlier studies on radio-proton spectral correlations
and proton-r iometer absorption correlations are combi-
ned to propose a real time prediction scheme for the
riometer absorption based on solar radio spectral infor-
mation.
1. INTRODUCTION
We have shown elsewhere (Bakshi and Barron, 1979, Bakshi and
Barron, 1978) the possibility of predicting the slope as well as
the magnitude of the proton peak flux vs. energy profile by using
as input certain characteristics of the U-shaped radio spectra. In
another study (Bakshi and Barron, 1976) we have also shown that
there is a very high correlation between certain features of the
proton spectrum and the observed Riometer Absorption. Combining
these results allows us to propose a real time, quantitative
prediction scheme that relates the Riometer Absorption to the
Radio Burst data. The above mentioned studies dealt with the major
events of the twentieth solar cycle. The prediction scheme, based
on these data can be tested by the coming events of the current
cycle.
2. RADIO-PROTON CORRELATIONS
-6
For the proton integral spectrum I (>E MeV) = AE , we have
shown (Bakshi and Barron, 1979) that the slope can be predicted
from the real time radio data in the form
1.185
{log10(o),/w2) }
t 0.A5 (1)
D3 - 26
where w, is the frequency at which the high-frequency branch of the
radio U spectrum attains its maximum flux density and 002 is the
frequency at which the U spectrum attains its minimum flux density.
The correlation coefficient for this power law form was r ^ 0.77-
The complete proton spectrum can now be obtained if we can
predict the magnitude I (>E0MeV) = I eq at any value of E0. A
convenient choice is EQ = 10 MeV. We have shown (Bakshi and Barron,
1978) that the time and frequency integrated radio energy e is a
good predictor of the proton flux magnitude \]q, after being
corrected by a locational factor:
l10 = (0.115) e1'77 e"3A (5. 1^)±1 , (2)
where e, in units of 10"'^ Joules m"^, is obtained by a time
integration of the incident radio flux density at various discrete
frequencies, followed by a frequency integration over a standard
range from 606 to 8800 MHZ, and A is the magnitude in radians of
the angular distance of the flare location from the standard re-
ference longitude 57°W. The last factor in Equation (2) represents
the standard deviation. The correlation coefficient for the data
of the twentieth solar cycle which led to Equation (2) was r % 0.80.
A slightly different formula can also be used (Bakshi and Barron,
1978), which relies in addition on the average proton energy factor
p = 3/(3-1), where B is to be predicted by Equation (l).
3. PR0T0N-RI0METER CORRELATIONS
Empirical connections between riometer absorption and solar
protons during PCA events have been extensively studied. Most
studies (Potemra, 1972, Cormier, 1973, Stroscio and Sellers, 1975)
have considered a relation of the form R = m[l(>E0)]?, where R
measured in dB is the observed riometer absorption (generally at
30 MHZ) , I (>E0) is the corresponding flux of protons with energies
greater than some specified energy E0 and m is an empirically
determined proportionality constant, which assumes different values
for different threshold energies E0.
There is one obvious shortcoming in schemes such as these
which rely entirely on the flux-magnitude of the protons. Consider,
for instance, two events which give rise to the same flux I (>EQ) ,
but which have significantly different energy profiles, characterized
by significantly different slopes 3. It is reasonable to expect
that the event with the harder proton spectrum (small B) will give
rise to a larger riometer absorption, since its protons, on the
average, carry more energy than is the case for the event with a
softer spectrum (large G) . The above mentioned schemes, however,
cannot distinguish between such events. To rectify this, it is
necessary to take into consideration the slope as well as the
magnitude such as l«g for the proton profile. We have developed,
D3 " 27
and tested (Bakshi and Barron, 1976), a simple empirical formula for
the proton-r iometer correlation along these lines.
The riometer absorption R is correlated with the proton variable
log 1 10 + a log p where p is a measure of the average energy for the
proton flux, and a is an adjustable parameter, varied to optimize
the correlations, a = 0 corresponds to ignoring the energy effects;
a = 1 corresponds to using the full energy flux rather than the
number flux for the protons. The detailed selection criteria have
been set forth in (Bakshi and Barron, 1976). Only the strong events
with I io > 100 protons cm~2 sec"' ster"! were considered in this
study. The riometer readings were generally greater than 2dB. If
we assume that the proton profile is well represented by a single
slope 8, the energy factor p is given by p = 3/(3-1). For approx-
imately a dozen events for the period 1967*72, characterizing the
peak of the twentieth solar cycle, the best fit straight line is
found (Bakshi and Barron, 1976) to be
R = a{ log]0 ' 10 + a lo9l0 P^+ b> (3a)
with the best correlation coefficient (r % 0.97) obtained for a =
0.^2. The corresponding standard deviation is a = t 1.1 dB and
the coefficients a and b are given by
a = 7.81, b = -13.36, (a = 0.42). (3b)
It should be noted that the correlation coefficient shows only a
slight variation in the range a = 0.2 to a = 0.6. It is also
interesting to note that the square root type formula, used in
other studies (Potemra, 1972, Cormier, 1973, Stroscio and Sellers,
1975), would lead to almost twice as large a standard deviation
a = 2.05 dB and a significantly lower correlation coefficient
(r % 0.90).
k. RADI0-RI0METER PREDICTION SCHEME
It is now possible to combine Equations (l) to (3) to
obtain a real time quantitative prediction for the riometer absorp-
tion R from various features of the radio spectrum. Ijq is predicted
by Equation (2) using the time and frequency integrated radio
energy e and the flare location A. p = 8/(3~l) is predicted by
Equation (l), using the radio frequency ratio 003/0)2- Then Equation
(3) provides a prediction for R in terms of the real time flare
parameters. It is necessary to observe the radio flux profiles at
several different frequencies as a function of time in order to
determine e. It is also necessary to have real time integration
routines to carry out the time and frequency integrations. By
noting the peak flux density at each frequency, one can determine
whether a U-spectrum has been achieved, and if so, what the peak
(013) and dip (012) frequencies are. All of these operations are
D3 - 28
within the present day technological capabilities, and in fact some
of these operations are already being carried out at observatories
like the Sagamore Hill Observatory. It should be noted that besides
these radio observations, one also needs the flare longitude in order
to correct for the attenuation effects according to Equation (2).
5. DISCUSSION
The prediction scheme described above rests on empirically
established relationships, Equations (l) to (3). These ideas for
using such relationships, which emphasize the radio-spectrum energy
or the proton-spectrum energy as correlation variables are soundly
based on general physical considerations, and thus do not depend
on any particular, detailed theoretical models. Such models could
lead to a more detailed understanding of why the relationships
work and could also provide useful refinements that might improve
the correlations.
Some of the limitations of the studies described above can
be easily removed:
(i) The proton riometer correlation equation (3) is restricted
to strong events, with 1 i o > 100 protons cm~2sec
ster~l. Additional events with lower thresholds for I i q
such as >50 or >10 protons cm~2sec~l ster~l should be
examined to extend the range of applicability of
Equation (3) •
(ii) The radio-proton correlation in Equation (l) leads to
slope values near or less than unity for radio frequency
ratios wo/u)2 - 10. The corresponding values of the
energy factor p = 3/(3"l) are not meaningful, since the
(p,3) relationship is valid only if the proton spectrum
can be described in terms of a single slope for its
entire energy range. Usually the spectrum softens for
higher energies and if this is properly taken into
consideration, a more meaningful energy factor for such
events can be developed in terms of a two slope formula,
as shown in Bakshi and Barron, 1976. An appropriate
correction to Equation (l) has to be incorporated when
0)3/0)2 ^ 10.
(iii) We have been concerned here with the peak riometer absorp-
tion for a given event. However, the proton-r iometer
relation holds even as a function of time, as the event
unfolds. If one can develop a reliable prediction for
the time development of the proton fluxes at various
energies, it would, with the aid of Equation (3) provide
a corresponding prediction for the riometer absorption.
Further work on this topic is in progress.
D3 - 29
REFERENCES
Bakshi, P., and W. Barron (1976): Predicting riometer absorption
for solar radio bursts I. Correlations between proton spectra
and riometer absorption, Rep. AFGL-TR-76-OI66, Air Force Geophys
Lab., Hanscom Air Force Base, MA.
Bakshi, P., and W. Barron (1978): Prediction of proton flux magni-
tudes from radio burst data, Rep. AFGL-TR-78-OIOO, Air Force
Geophys. Lab., Hanscom Air Force Base, MA.
Bakshi, P., and W. Barron (1979): Prediction of solar flare proton
spectral slope from radio burst data, J. Geophys. Res. 8A 131-
Cormier, R.J., (1973): Thule riometer observations of polar cap
absorption events, AFCRL-TR-73-0060.
Potemra, T. A., (1972) Radio Sci . ]_, 571.
Stroscio, M. A., and B. Sellers (1975): The calculation of riometer
absorption and an approximate connection between riometer ab-
sorption and solar proton fluxes during nighttime PCA events,
AFCRL-TR-75-0469.
D3 - 30
A METHOD OF PREDICTING SKY WAVE FIELD STRENGTH
IN HF BANDS IN TROPICAL ZONE
0. P. Sehgal
A1 1 I ndia Radio
Simla, I nd ia
and
H. 0. Agrawal
All India Radio
Research Department, Indraprastha Estate
New Delhi 110002, India
1. INTRODUCTION
The values of the field strengths measured in our region did not agree
with the values estimated by well-known prediction methods such as those of
CRPL and RPU-9 of the United States and SPIM of France. AIR therefore de-
veloped its own method, popularly known as the AIR method for the prediction
of skywave field strength in HF bands in the tropical zone. The method was
developed as a result of extensive measurements conducted over almost a full
sunspot cycle of ionospheric absorption at New Delhi starting in 195^- The
method can be used with both manual calculations and computer programming. A
computer program has been written by J. A. Murphy (I969).
Of the many factors involved in the prediction of the skywave field
strength, the most important is the ionospheric absorption, particularly the
non-deviat i ve absorption suffered by the wave in traversing the D region.
Studies on the diurnal, seasonal and sunspot cycle variation of ionospheric
absorption were made in the Research Department of AIR on the basis of vertical
absorption measurements conducted on 5 MHz at New Delhi over a solar cycle (Rao
et al., I962). Based on practical observation, the formula for non-deviat i ve
absorption was determined and is given by the following expression:
635 n (1 + 0.0017 R12) sec $
L ' (f ± fL)* Ch(a, X)0-77
where L = ionospheric absorption
n = number of hops
Rl2 = 12 month running average sunspot number
<j> = angle of incidence at the absorbing layer
f = wave frequency
fi = longitudinal component of the gyrof requency
± = signs refer to ordinary (+) and extraordinary (-) wave compon-
ents
Ch(a,x) ■ Chapman function and is taken to be equal to sec x when x ^ 80.
On the basis of measurements of ionospheric absorption at night, a value
D3 " 31
of 2.5 db for the deviative absorption has been taken into account for calcu-
lating the nighttime field strength and also a polarization loss of 3 db has
been assumed. The AIR method (Rao, I969) gives a set of ten nomograms and the
skywave field strength of any circuit may be evaluated in an easy manner for
different possible modes of propagation through the ionosphere.
Field strength measurements made on AIR's regional shortwave transmis-
sions operating on 6-9 MHz bands indicate very good correlation between the
observed values and the values estimated using the AIR method. The differ-
ences were within ±3 db.
2. RECENT STUDIES
Some recent studies, however, indicated that the AIR method gives higher
absorption values on lower frequencies when the propagation is via the E re-
gion. Field strength measurements were therefore conducted on lower frequen-
cies at New Delhi and the results were compared with those estimated by the
AIR method and the CCIR first interim method. It was found that there was
better correlation between the observed and the estimated values of field
strength with the AIR method than with the CCIR first interim method when the
transmissions were via the F region. But the field strength estimated by both
methods did not agree with the observed values when the transmissions were via
the E region. A document indicating these results was submitted to CCIR in
1975 (Doc. 10/56, 197^-78).
At the interim meeting of Study Group 6 of CCIR in Geneva in February/
March 1976, Interim Working Party 6/1 proposed a second CCIR computer-based
interim method which is described in detail in CCIR Report 252-2 (Rev. '76).
This method is recommended for universal application and is based on a better
understanding of ionospheric characteristics and the experience gained in
using the first interim method. The main difference between this method and
the other known methods is in the evaluation of basic transmission loss, in
particular ionospheric absorption.
Field strength measurements were conducted by the Research Department of
AIR on lower frequencies at New Delhi during 197**~75 and 1976. The observed
values were compared with those estimated by the AIR method and the second
CCIR method (using manual computation). It was found that there was good
correlation between the observed values and those estimated using the second
CCIR interim method when the propagation mode is via the E or F regions. Us-
ing the AIR method, the correlation was quite good when transmissions were via
the F region. A document was submitted to CCIR in 1977 (Doc. 10/323, 197W8)
giving these results.
Further field strength measurements have been carried out at a number of
places in India on different frequencies and the observed values, when compared
to those estimated by the AIR method and the second CCIR method, indicate the
same trend. The observed and estimated values are shown in a scatter diagram
(see Figure 1). The results of the above studies on the comparisons between
the AIR method and the second CCIR method for single hop propagation via F-
region mode indicate that in a total of 61 cases of measurements taken at New
Delhi, Gauhati, and Trivandrum, deviations are within ±3 db in about 50 percent
of the cases by both the methods. However, the AIR method gave results within
±6 db in about 82 percent of the cases whereas the CCIR method gave results
within ±6 db in about 67 percent of the cases.
D3 - 32
ou
o
1 1 1 1
Predicted Field Strength Using A.I.R. Method
1
A
Predicted Field Strength Using C.C.I. R. Method
70
(Rep. 252-2 Rev. '76)
O
o A
AO y/
O A/
O £f
—
:L
o a/
S 60
a/o° a
ao^ y^° °
°~° V/V? AO A A
0
O O XA0 o A A
l_
0 / AAO °0 A
co
o £r
2 50
—
0/ O AO A
/ O AO A
—
<D
U_
o
o
°O^AA
TJ
/J, A A
(D
5 ° A0 A
>
0)
°s
0 0aA
.2 40
XA°
* A
-
o
s °
A
A
30
on
O
/ 6
A
1 1
1 1
1
20
30
40 50 60
Predicted Field Strength dB^i.
70
80
Figure 1. Observed and predicted field strength.
D3 - 33
3. CONCLUSIONS
Regarding a suitable field strength prediction method, our view is that
the method should be simple and easily applicable for day-to-day calculations
particularly for countries in the tropical zone who are mostly economically
weak and developing. The facilities of high speed computers are not generally
available to most of them. Hence a method which is capable of being applied
with simple aids like nomograms is most desirable. For propagation via F2
region the AIR method is quite appropriate due to its simplicity, proven
accuracy and availability of nomograms. On the other hand the second CCIR
method is cumbersome and requires the use of a high speed computer. The com-
puter program is still not available. It has also to be put to elaborate
practical tests for its applicability in tropical regions. In addition,
nomograms, etc., are yet to be developed to apply this method for quick evalu-
ation of field strength values.
REFERENCES
CCIR Doc. 10/56, 197^-78.
CCIR Doc. 10/323, 197^-78.
Murphy, J. A. (1969): Computer programme for the evaluation of field strength
by AIR prediction method. Radio and Space Research Station, Slough,
England .
Rao, M. K., Mazumdar, S. C, and Mitra, S. N. (1962) : J.A.T.P., 2k,
pp. 2^5-256.
Rao, M. K. (I969): Nomographs for Calculation of Field Strength, Journal
of Institution of Telecomm. Engrs (India), 15, p. 729.
D3 - lh
UNPREDICTED VARIATIONS IN D-REGION RESPONSE
TO SOLAR X-RAY EVENTS
R. H. Doherty
Seasonal and latitudinal changes in the D-region response
to solar X-ray events have been observed using low frequency pulse
propagation. These pulse signals (Loran-C) have been monitored
over reciprocal paths. The once reflected sky wave signal is se-
lected by sampling the pulse at the proper time. Also, the paths
are long enough to greatly attenuate the ground wave signal.
The day time signals show considerable phase and amplitude
sensitivity to sudden ionospheric disturbances (SID) produced by
solar X-rays. The changes observed are not always the standard
phase advance and amplitude increase normally seen on VLF cw sig-
nals. Three paths at roughly 25°, 35° and 60°N latitude have been
statistically examined for a one year period. On a statistical
percentage basis, phase advances are compared with phase retarda-
tions and amplitude increases are compared with amplitude decreases.
Two individual SID events occurring at different times on the
same day are observed on four different paths to show how changes
of solar zenith angle and latitude of the reflection point can in-
fluence the propagation effects observed.
The variations with latitude, the variation with season, and
the variation with solar zenith angle all suggest that during a
SID event the amplitude changes occur at a different ionospheric
height than do the phase changes.
INTRODUCTION
Data from three reciprocal propagation paths were analyzed for the one
year period from July 1, 1969 through June 30, 1970. The three paths chosen
for this study were Hokkaido, Japan to Yap Island and reciprocal with a mid-
point at 26°N latitude; Jupiter Inlet, Florida to Nantucket, Massachusetts
and reciprocal with a midpoint at 34°N latitude; and Attu Island (in the
Aleutian Islands of Alaska) to Port Clarence, Alaska and reciprocal with a
midpoint at 60°N latitude.
It has been recognized for some time (Doherty 1963) that although the
usual observed effect for an SID as seen on VLF cw signals is a phase ad-
vance and an amplitude increase, LF pulse signals that are only once reflec-
ted from the ionosphere can show phase retardations or advances and amplitude
increases or decreases in all possible combinations. The LF signals from
D3 - 35
Tashkent to Delhi (Suurahmanyam, et. al . , 1974) have been evaluated for these
type of effects. The use of several paths at different latitudes all analyz-
ed over a similar period has apparently not been previously reported.
The particular effect produced by a particular solar flare can be shown
to depend on the intensity and wavelengths associated with the X-rays pro-
duced by that flare. A large flare can produce one effect and a small flare
another effect on any given path for any given day. It was anticipated, how-
ever, that statistically over a season and for paths at different latitudes
the variation of the intensity and wavelengths of flares could be averaged
out. This should be particularly true if only the gross effects of the
flares were considered.
Consequently, a study was made over a period of one year on the percen-
tage of total number of SID's that produce phase advances or amplitude en-
hancements. The remainder of the flares in this study produced phase retarda-
tions or amplitude decreases or both. Actually, the phase and amplitude
statistics are treated separately, but it is obvious from the results that
there is a strong tendency for phase retardations and amplitude decreases to
occur together.
1. STATISTICAL VARIATIONS FOR ONE YEAR OVER THREE PATHS
The statistical percentage variations presented in Figures 1 through 8
are arranged so that all of the phase information is presented in Figures 1
through 4 and all of the amplitude information is presented in Figures 5
through 8. A direct comparison of the phase effects to the amplitude effects
can be obtained in each case by comparing Figures 1 and 5, 2 and 6, 3 and 7,
or 4 and 8.
Figure 1 shows the seasonal variation in the percentage of phase advances
for the three paths indicated above. This figure shows that there is a def-
inite tendency for flares to produce retardations during winter months, par-
ticularly at the higher latitudes. This result suggests changes in the
ionospheric D-region with latitude and season. Evidently the ionospheric D-
region is reacting to the flare X-rays differently at some times than at
others. In an attempt to determine if this effect was merely a manifestation
of solar zenith angle changes, the percentages of phase advances were deter-
mined as a function of the solar zenith angles. In Figure 2 the data from
all three paths were combined, but the percentages were evaluated for pre-
dominantly summer months (April through September) and predominantly winter
months (October through March). The rapid drop off of the winter curve and
the crossing of the summer and winter curves in Figure 2 appears to be pri-
marily related to the fact that winter and summer conditions are quite
different for the 60°N latitude path. However, the difference in slope for
the summer and winter periods may well be an indication of a smoothly changing
D-region as a function of latitude, particularly in winter months, which is
not just a manifestation of the larger solar zenith angles occurring at these
times.
In Figures 3 and 4 the percentages were derived for each path separately
D3 - 36
100
80
£ 60
4>
a.
40
20
26° N Latitude
262 SIDs
34° N Latitude
352 SIDs
60° N Latitude
289 SIDs
JAN-FEB MAR-APR MAY-JUN JUL-AUG SEP-OCT NOV-DEC JAN-FEB
Figure 1. Percent of flare events with negative phase changes (phase
advances) as a function of season.
100 —
80
c
o
2 60
0)
Q_
40-
20-
1
1 1 1 1
1 1 1
""V^N
\ \
Months April through
—
September (Summer)
—
521 SIDs
\
\
^
\
>l
\
-
Months October
March (Winter)
through \
\
\
\
-
380 SIDs
1
1 1 1 1
i i i
Figure 2
£19 20-29 30-39 40-49 50-59 60-69 70-79 ^80
Solar Zenith Angle
Percent of flare events with negative phase changes
(phase advance) in the given solar zenith angle ranges
for all three propagation paths.
D3 " 37
I
1 1 1
1 1 1
1
100
'..
™ *v» 26° N Latitude
\
"V*. 108 SIDs
\
>*
80
-
•
•
•
•
34° N Latitude
1
•
-
c
S 60
•
0.
159 SIDs
•
•
•
•
•
\
-
40
60° N Latitude ^"\
113 SIDs X
20
I
1 1 1
\
n
1 1 1
1
£19
70-73
280
Figure 3.
20-29 30-39 40-49 50-59 60-69
Solar Zenith Angle
Percent of flare events with negative phase changes
as a function of solar zenith angle for three paths
at different latitudes for the winter months October
through March.
100 —
80 —
c
01
i! 60
40
20-
1 1 1 1
1 1
1
•
26° N Latitude
•
•
154 SIDs
•
•
•
•
•
-
34° N Latitude \
191 SIDs
-
•
• •
60° N Latitude yT
\ .•
—
176 SIDs y^
V
—
1
1 1 1 I
1 1
1
sl9
20-29
30-39
60-69
70-79
40-49 50-59
Solar Zenith Angle
Figure k. Like Figure 3 except for months April through September,
D3 - 38
100
80-
c
a
Z 60
a.
40-
20-
1 1
1
1 1
1 1
/*
x^X\ \
.4
\ \ \
26° N Latitude
34° N Latitude .•* /
^, •
^. •
^. •
^ •
\ •
v 265 SIDs
\
354 SIDs / / J
\ •
\ •
\
•••' * /
i •
\ •
\ •
\
/ / /
\ \
/ / /
\ \
•• ' /
*-... \
••' / /
••v.
/ /
V \
/ 1
60° N Latitude
283 SIDs
\ \
/ 1
1
1 1
1 \l
° JAN-FEB MAR-APR MAY-JUH JUL-AUG SEP-OCT NOV-DEC JAN-FEB
Figure 5- Percent of flare events with amplitude enhancements
as a function of season.
100
80
c
o
e 60
40
20
\
Months April through
September (Summer)
520 SIDs
Months October through ^
March (Winter) \
382 SIDs *
\
\
\
V
<I9
20-29
70-79
>80
Figure 6
30-39 40-49 50-59 60-69
Solar Zenith Angle
Percent of flare events with amplitude enhancements
as a function of solar zenith angle.
D3 - 39
100
80
Q.
60
40
20
\ \
26°NLotltude \ '.
110 SIDs \ \ y\
\\
60° N Latitude
110 SIDs
..* 34° N Latitude
161 SIDs
J_
J.
J_
I
£19
Figure 7
20-29
30-39
60-69
70-79
40-49 50-59
Solar Zenith Angle
Percent of flare events with amplitude enhancements
as a function of solar zenith angle for the months
October through March (winter).
80-
« 60
a.
40-
20
1 1
1 1 1
1 1
1
26° N Latitude
\ "'•• >*
155 SIDs
-
v~
•»..% 34° N Latitude
\ 193 SIDs
•
•
-
60° N Latitude^X.^^
•
- •
172 SIDs
-
^^«
-
1 1
1 1 1
1 1
1
0
519
Figure 8,
20-29
30-39
70-79
:80
40-49 50-59 60-69
Solar Zenith Angle
Percent of flare events with amplitude enhancements
as a function of solar zenith angle for the months
April through September (summer).
D3 - **0
for both the winter and summer periods. The data plotted in these figures
seem to emphasize the effects observed at 60°N latitude are considerably dif-
ferent from those observed at 26° and 34°N latitude, but this might be antici-
pated since the change in one case is only 8° whereas, in the other case, it
is 26°. The analysis presented herein seems to be suggestive of D-region
changes but inadequate in scope and number of paths analyzed to make quanti-
tative statements about the D-region changes that may have occurred. The
data particularly in Figure 3 and to a lesser extent in Figure 4 show that
there appears to be a latitude effect for both the winter and summer periods.
The data in Figures 2 and 3 suggest that there is a dependence on solar zenith
angle in addition to latitude or season. This is true since there is nearly
always a tendency for phase retardations to occur at higher zenith angles
irrespective of the other factors. There is a suggestion in Figure 4 that at
higher latitudes during the summer months this trend may reverse. This point
should merit further study.
Figure 5 shows the results of an analysis similar to that presented in
Figure 1. In this case the percentage of amplitude enhancements are plotted
versus the seasonal periods. Again it can be seen that there is a strong
seasonal variation. It is interesting to note that the seasonal variation of
these amplitude percentages does not change as much with latitude as the
phase percentages did. This is consistent with the previously reported fact
that the diurnal amplitude variations do not change as much with latitude as
the diurnal phase variations do (Doherty, 1968). These facts also suggest
that there is a different region of the ionosphere controlling the signal
amplitude than that controlling the signal phase. Figure 6 shows the ampli-
tude effect versus the solar zenith angle for the three paths combined with
the two periods similar to Figure 2 for the phase. The winter and summer
curves do not cross in this case as they did in the phase analysis, again
suggesting a different portion of the ionosphere influencing the phase and
amplitude of the signals. Figures 7 and 8 again represent the results of the
paths treated separately. In this case nearly all of the curves demonstrate
a greater tendency for the amplitude to decrease as the solar zenith angle
increases. The solar zenith angle changes, the changes in the latitude of
the path, and the seasonal changes all seem to work consistently together in
their effect on the percentage of amplitude events that show a signal en-
hancement.
2. SHORT TERM VARIATIONS OF SID SIGNATURES AND DIURNAL CHANGES
The statistical analysis described above suggests that there is a season-
al change, a latitudinal change, and a change in the D-region with solar
zenith angle. It also suggests that at any one time there might be a trade
off between latitude changes and solar zenith angle changes. Consequently,
certain paths that lent themselves toward checking such effects were studied;
and several events with this type of trade off were found. One such example
is shown in Figures 9 through 16. On May 15, 1970, a solar flare occurred
just after 1900 GMT (approximately noon at Boulder, Colorado). SID effects
were observed on four paths as shown in Figures 9 through 12. The solar
zenith angle from the midpoints of each of these paths was less than 35°.
Figure 9 shows the effect observed for the path from Jupiter Inlet, Florida,
to Nantucket, Massachusetts, where the latitude of the midpoint was 34°. The
D3 - k\
0)
a>
k.
a>
Q
J2
a>
'o
O
1
1
* =34°
Lot. =34°
± \
90° \
T
May 15,
1970
100 kHz Loran-
•C
_L
Jupiter,
Fla. to Nantucket, Mass.
10 dB
_T J
1
1
1800
1900
2000 UT
Figure 9.
360
a>
Q
180 -
fj 40
a
o
1 1
1 1
1 1 1
y =22°
Lot. =34°
_ .
-
-
-
-
May 15, 1970
100kHz Loran-C
-
—
Jupiter, Fla. to Boulder, Colo.
-
-
^y-^_
-
1 1
1 1
1 1 1
oL
1800
1900
Figure 10,
D3 - k2
2000 UT
360
en
0
CD
g 180
a
¥ =26°
Lot. =38°
3
=1 40
o>
Q
May 15, 1970
100 kHz Loron-C
Cape Fear, N.C. to Boulder, Colo. _
1
1600
1900
Fi gure 1 1
2000 UT
36U
1 1 1
I 1 i I
¥ = 30°
_
Lot. = 42°
I 180
a>
a
n
(V
£ 40
a>
O
May 15,1970
lOOkHzLoran-C
Nantucket, Mass. to Boulder, Colo.
M.-,iyyV, N ,n, - /
1
1800
1900
Figure 12.
2000 UT
D3 - A3
0>
CD
Q
J_
90c
T
¥ =69°
Lot. = 34°
May 15, 1970
100 kHz Loran-C
Jupiter, Fla. to Nantucket, Mass.
2200
Figure 13
2300 UT
360
¥ =56°
Lot. =34°
O
0L
May 15, 1970
100 kHz Loran-C
Jupiter, Fla. to Boulder, Colo.
H 40
o
2200
2300
Figure 1 k
D3 - kk
0000 UT
360
0)
a, iflo
Q
♦ = 56°
Lot. = 38°
3
=5 40
Q
Moy 15, 1970
100kHz Loran-C
Cape Fear, N.C. to Boulder, Colo.
2200
2300
Figure 15
0000 UT
360
a>
Q
180 -
0L
a
% 40
Q
1 1
1 1 1 1 1
* = 59°
Lai. =42°
-
-
—
-
-
-
May 15,1970
IOO kHz Loran-C
-
-
Nantucket, Mass. to Boulder, Colo.
—
1 1
-
1 1 1 1 1
2200
2300
Figure 16.
0000 UT
D3 - *»5
phase advance and amplitude increase were comparable to those shown in Figure
10 for the path from Jupiter Inlet, Florida, to Boulder, Colo., with a mid-
point latitude also equal to 34°. (Note the difference in vertical scales
between Figures 9 and 10). The signal observed between Cape Fear, North
Carolina and Boulder, Colorado, where the latitude of the midpoint equaled
38°, (Figure 11) showed a somewhat smaller effect; and the signal observed
between Nantucket, Mass., and Boulder, Colo. (Figure 12), where the latitude
of the midpoint equaled 42°, showed a phase retardation rather than a phase
advance. Three hours later when the solar zenith angle for the Jupiter Inlet,
Florida, to Nantucket, Massachusetts, path was 69°, a second flare occurred.
Figure 13 shows a phase retardation was observed on this path, even though
the latitude was 34°. Figure 14 shows that a phase advance occurred on the
path from Jupiter Inlet, Florida, to Boulder, Colorado, latitude = 34°, where
the solar zenith angle was only 56°. Figure 15 shows a smaller phase advance
on the path from Cape Fear, North Carolina, to Boulder, Colorado, latitude =
38°, zenith angle = 5G°. Figure 16 shows a phase retardation again on the
path from Nantucket, Massachusetts to Boulder, Colorado, latitude = 42°,
zenith angle = 59°. It can be seen by referring back to Figure 13 that the
effect observed over this 34°latitude path is nearly the same as the effect
observed for the 42°latitude path (again note the difference in the vertical
scales between Figures 13 and 16). This example gives a s/ery graphic picture
of the trade off between latitude changes and solar zenith angle changes that
can occur at times.
In addition to the flare effects discussed above pronounced diurnal
changes occur, primarily at sunrise and sunset, that are highly repetitive
from day to day (Doherty 1967, 1968). These diurnal variations are different
at different latitudes and change with season in a manner similar to the flare
effects described above. Since there is little reason to anticipate that the
night time D-region should change appreciably with season or latitude, it
should be possible to relate the diurnal variations of the phase and ampli-
tude with the solar flare observations to deduce a meaningful statistical
model of what the daytime D-region looks like and how it changes with lati-
tude, season, and solar zenith angle.
The diurnal variations that have been reported previously indicate that
the phase of the LF pulse sky-wave signal follows a cosine chi pattern during
the day at low latitudes for all seasons. At higher latitudes, it follows a
cosine chi pattern in the winter, but a trapazoidial pattern with changes at
sunrise and sunset in the summer. The measurements further show that the
amplitude of the signals generally follow the trapazoidial pattern for all
seasons and all latitudes. This again suggests a different portion of the
ionosphere is controlling the phase and the amplitude. It is also interesting
to note that the seasonal phase pattern shown in Figure 1 changes with lati-
tude as does the diurnal pattern, but the seasonal amplitude pattern shown in
Figure 5 does not change with latitude as is true of the diurnal amplitude
pattern.
CONCLUSIONS
The results of this analysis suggests that any predicted D-region pro-
files will need a variation with season and latitude that can produce these
D3 - ^6
observed low frequency SID effects. The analysis shows that for the three
northern latitude paths chosen, solar X-rays tend to attenuate the LF signals
in the winter and enhance the signals in the summer. At the lowest latitude
solar X-rays produce nearly 100% phase advances, whereas, at the highest lati-
tude, phase retardations occur more than 50% of the total time, and nearly
100% during winter months. Seasonal variations are observed on all three of
the paths with amplitude decrease and phase retardations more common during
winter months. The non-correlation between the phase variations and the
amplitude variations strongly suggest that a different part of the D-region
is controlling the phase changes and the amplitude changes of these signals.
REFERENCES
Doherty, R. H. (1963): Oblique incidence pulse measurements at 100 k c/s.
AGARD ograph 74, Pergamon Press, 133-147.
Doherty, R. H. (1967): Oblique incidence pulse measurements at 100 kHz
pulses. Radio Science, Vol. 2 (new series). 645-651.
Doherty, R. H. (1968): Importance of associative detachment and dissocia-
tional attachment in the lower ionosphere as shown by LF radio measure-
ments. J.C.R., 73. 2429-2440.
Subrahmanyam, C. V., Sastri, J. Hanumatr, and Desphande, S. D. (1974): Study
of solar flare signatures on If field strength over Tashkent-Delhi Path.
Indian Journal of Radio and Space Physics, Vol. 3, 153-157.
D3 - M
SECULAR VARIATION OF OCCURRENCE RATE AND DISPERSION OF LOW-LATITUDE
WHISTLERS DURING THE SOLAR CYCLE NOS.19 AND 20
Y.Tanaka, M.Hayakawa, J.Ohtsu and A.Iwai
Research Institute of Atmospherics, Nagoya University,
Toyokawa, Aichi, 442, Japan
On the basis of the measurement during the solar cycle Nos.19 and
20, the long-term variations of the occurrence rate and dispersion
of whistlers at low latitudes are investigated in relation with
the solar and geomagnetic activities. The whistler data used for
the study were obtained at Wakkanai(geomag.lat.35.20N) ,Moshiri
(34.1°) ,Toyokawa(24.1°) and Sakushima(24.1°) . First we find a very
high correlation coefficient of ~ 0.9 between the dispersion at
Wakkanai-Moshiri with the sunspot number, as in the case of the
foF2. Then it is found that the occurrence shows a weak positive
correlation with the geomagnetic activity, while it shows an obs-
cure inverse one with the sunspot number. The occurrence is found
to be well expressed by a linear equation of the geomagnetic acti-
vity and sunspot number based on the least square fit and then the
correlation coefficients between the occurrence frequency at Wakka-
nai-Moshiri and Toyckawa-Sakushima and that expected from the equ-
ation are found to amount to rather high values of more than o.7,
implying that the occurrence number can be determined by the joint
influence of both activities.
1. Observation of whistlers in Japan
The routine-based observation of whistlers has been continued since 1957
at a low latitude station (Wakkanai , July 1957-Nov. 1962 ;Moshiri, since Dec. 1962)
and also at a still lower latitude station (Toyokawa, July 1957-June 1966; Saku-
shima, since Feb. 1967) . The antenna site was changed from Wakkanai to Moshiri
and also from Toyokawa to Sakushima so as to keep the observation in good con-
ditions since we encountered the increase of artificial noises at the former
sites. The observation had been made during two minutes starting from 20 and
50 min. every hour, but we are now carrying out the observation only during 50-
52 min. every hour. The general view concerning the observation of low-latitu-
de whistlers and their characteristics is given in the recent review paper by
Hayakawa and Tanaka(1978) .
D3 - L\S
2. Characteristics of occurrence number
Fig.l shows the secular variation of the occurrence rate at Toyokawa-Saku-
shima. Dot marks in the figure indicate the daily average of the occurrence
number per month. In obtaining the daily average per month we have excluded
the whistlers which are clearly indentified as "long". To make clear the solar
cycle variation in a more definite way we have attempted to exclude the season-
al dependence of the occurrence number and the effect due to different obser-
ving period as follows. The daily average in each month is normalized by the
mean of the daily average for the relevant month at each site,Toyokawa or Saku-
shima, throughout the solar cycles 19 and 20 (we call it the "normalized occurr-
ence rate" , although not shown in the figure) . Then the running mean of normali-
zed rate during 6 months before and 6 months after the relevant month is shown
by a cross mark in the figure. Fig. 2 is the similar result for higher latitude
station (Wakkanai-Moshiri) , which is drawn in the similar way as in Fig.l.
The exact estimation of the absolute value of occurrence number is, in most
cases, very difficult because of the dependence of occurrence on the circumstan-
ces of radio noises at the observing site. So the simultaneous observation at
both old and new sites in a certain overlapping period is highly required, even
if there were not present the abrupt depletion in the observing conditions due
to the increasing artificial noises at the old sites. We did not make such si-
multaneous observations, but we will be able to treat the running means at both
stations quite equally since we notice a very smooth transition in the varia-
tion during the removal, as shown in Figs.l and 2. In the case of Toyokawa-Saku-
shima stations in Fig.l, the observation was interrupted for seven months follo-
wing the movement of the stations, but, nevertheless, it may be reasonable to ima-
gine a relatively smooth transition in the normalized occurrence rate around
that period with taking into account the transition at Moshiri in the same pe-
riod. We have been monitoring, in a regular interval, the observing system in-
cluding the antennas, pre- and main amplifiers and so we think that the observ-
ing conditions have been kept well in an isolated village of Moshiri as well as
in a noise- free island of Sakushima up to date since the removal.
3. Characteristics of dispersion
Fig. 3 shows the secular variation of the monthly mean (i.e. average per
month) of dispersion and its running mean at Wakkanai-Moshiri. The range of dis-
persion is restricted to 25-90 secl/2. The difference in latitude between the
two stations is too small to affect the results. The occurrence rate is found
to show a great decrease in summer at Toyokawa-Sakushima as shown in Fig.l, and
the available data are too few to determine the mean values at Toyokawa-Saku-
shima. So we study only the secular variation of dispersion at Wakkanai-Moshi-
ri.
4. Secular variation of sunspot number, geomagnetic activity and fnF2
Fig. 4 illustrates the solar cycle variation of the daily average of sun-
D3 - ^9
5.0 _
4.0 -
3.0
2.0
h 1.0
• daily average
•
Toyokawa
" 4 minutes
no
observation
* running mean
•
T
Sakushima
2 minutes
■
every hour
4 minutes
-
-
•
* • A '
•
•
. .
•
• •
•
* • *
• . • . « *
•
• •
•
• • * /
•
•
•
•
*
•
•
•
• *
• • t '
• • •# •*
•m m
• •
m
R
•
•
*
•
- 1 - ■ *'*-- ■— ■-
i i.; i..
■•Vfi.
._ .^wrv*
•
1000
100
10
o
s
I
5
1957 58 59 1960 61 62 63 64 65 66 67 68 69 1970 71 72 73 74 75 76 1977
Fig.l Secular variation of whistler occurrence rate at Toyokawa-Sakushima.
•
daily average
5.0
Wakkanai
1
1
Moshiri
1
■
K
running mean
4 minutes
4 minutes
-*-
!
Moshiri ,
1
i
2 minutes
every hour
4.0
• •
• •
• •
•
•
*
• m
• ••
•
3.0
•
" .
•.*.
• • • . 4 •
•
4^ •
. • •
•
•
>••
• • •
••
•
2.0
' . • »
•
. * m
f
•
• •
•
•
•
* • «
•
•
• A • .
•
•
•
•
'./
1.0
• • • ■ • •*.
■Vsat.
•
•
«
*
• V
•
%■
0
1000
iao
10
1957 58 59 1960 61 62 63 64 65 66 67 68 69 1970 71 72 73 74 75 76 1977 ■
Fig. 2 Secular variation of whistler occurrence rate at Wakkanai-Moshiri.
4J
c
8
u
I
V
o
c
«
D3 - 50
1/2
Dispersion (sec ' )
70
60
50
40
30
20
• monthly mean at Hoshiri,N«Jckanai
> running mean
mmrn. •
•pT. '}
I I I I
J— t-
■ A I i
I I I I I I I
1957 58 59 I960 61 62 63 64 65 66 67 68 69 1970 71 72 73 74 75 76 1977
Fig. 3 Secular variation of dispersion at Wakkanai-Moshiri
1.0 1
0.9 •
0.8 .
0.6 .
0.3 -
0.2 -
0.1 .
• ••Monthly mean of £oF2 at midnight
■ XKDaily average of Cp index per month
Daily average of sunspot number per month
r 200
■ • ■ • ■ ■ ■ ■ I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' 1 ' I ' I ' I ' I ' 1 '
1957 58 59 1960 61 62 63 64 65 66 67 68 69 1970 71 72 73 74 75 76 1977
Fig. 4 Secular variations of the monthly mean of daily sum
of sunspot number, the monthly mean of Cp index and
monthly median value of midnight foF2 at Wakkanai.
D3 - 51 '
spot number per month, the daily average per month of the Cp index as a good
measure of geomagnetic activity (Kane, 1976) , and the monthly median value of
foF2 at midnight measured at Wakkanai. These three quantities are also express-
ed in the form of running means.
5. Correlation between the whistler characteristics and solar and geomagnetic
activities
First we simply study discuss the association of the dispersion with solar
activity. A comparison between Figs. 3 and 4 shows that there exist very close
relationships of the variations of the running means of dispersion and of foF2
with the sunspot number. We have found a surprisingly high correlation coeffi-
cient of 0.92 between the dispersion and solar activity and also a higher
value of 0.98 between the foF2 and solar activity, as summarized in Table 1,
implying that the magnetosphere is less sensitive to the long-term variation
of solar activity than the ionosphere, as shown by Hayakawa et al. (1971) . The
similar positive correlation has already been found on the basis of whistler
data at Wakkanai during the International Geophysical Years by Kimpara (1962a)
and during the solar cycle 19 by Hayakawa et al. (1971) . Based on the whistler
data at Poitiers during the solar cycle 19,Bouriot et al. (1967) have investi-
gated the solar cycle variation of the plasmaspheric electron density at middle
latitudes , and obtained the positive correlation between them.
Table 1 INTER-CORFELATiaSI BETWEEN VARIOUS PAPAMETERS
Whistler Observation
Sunspot
Number
Cp index
BjCp - 32sn
Station
Data
Toyokawa-Sakushima
Occurrence
-0.371
0.511
0.724
Wakkanai-Moshiri
Occurrence
-0.379
0.483
0.759
Wakkanai-Moshiri
Dispersion
0.917
^^^
Wakkanai
foF2
0.977
^-^^
Now we discuss the variation of occurrence rate in more details. Whistler
activity is specified either by the mean number of whistlers per unit time
("occurrence rate") or by the percentage pf periods containing whistlers ("per-
centage occurrence"). Either measure of whistler activity includes the effect
of thunderstorm activity as well as that of propagation conditions. Consider-
ing that if a propagation path existed for one whistler, then other nearby ligh-
tning discharges could also produce whistlers, the percentage occurrence seems
to be a better measure owing to its less dependence on the thunderstorm acti-
vity. However, actually no significant difference was found between the two
D3 - 52
measures (Allcock, 19 66 ) . Then there is no evidence suggesting distinct correla-
tion between the solar activity and thunderstorm activity around the conjugate
region of our stations in the southern hemisphere (Markson, 1971) . Therefore it
is thought that there is very little possibility to include the effect of thu-
nderstorm activity during the process of obtaining the running means from the
normalized occurrence rate. On this reasoning the secular variation of the
occurrence rate shown in Figs.l and 2 may be discussed only from the stand-
point that such long-term solar cycle variations are attributed to the varia-
tions in the propagation conditions (Hay akawa and Tanaka,1978) .
There are a few papers dealing with the association between the whistler
activity and solar and geomagnetic activities. Kimpara (1962a) found a surpris-
ingly high negative correlation over -0.9 on the basis of data during 4 years
from July 1957, and later Hayakawa et al. (1971) have noticed a small inverse
correlation ranging from -0.3 to -0.4 by making use of the data during the so-
lar cycle No. 19. A similar negative relation was found by Corcuff et al. (1966)
between the whistler activity at Poitiers and sunspot as well as geomagnetic
(Ap) activities using the data during 1957-1965.
Thus the general trend of inverse correlation between the occurrence rate
and solar activity is apparently recognized over either a portion of the solar
cycle No. 19 or the whole one solar cycle. Such an inverse correlation may be
understood in terms of the increase in ionospheric absorption of VLF waves
during active solar periods (Hayakawa et al.,1971). A small negative correlation
coefficient of -0.371 is obtained between the occurrence at Toyokawa-Sakushima
and sunspot number (see Table 1) throughout the solar cycles 19 and 20. The co-
rresponding value for Wakkanai-Moshiri is -0.379. These small correlations may
suggest that the long-term variation of occurrence rate cannot be interpreted
by the effect of solar activity alone and there exist some other factors con-
tributing to the occurrence. It seems to us that the most promising factor is
the geomagnetic activity. Enhanced whistler activity has been found during geo-
magnetic disturbances (Kimpara, 1962b; Hayakawa et al.,1969; Tanaka and Hayakawa,
19 73a, b) . The secular variation of the geomagnetic activity represented by Cp
index (Kane, 19 76) is given in Fig. 4, which shows an oscillation whose period is
roughly half of one solar cycle. Enhanced geomagnetic activities are seen to
be nearly in phase with increased occurrence of whistlers as clearly seen from
the comparisons of Figs. 1,2 and 4. For example, we can identify the simultaneous
enhancements in both occurrence and geomagnetic activity at 1959-1960,62-63,
67-68, and 72-74. Then we obtained the correlation coefficients of ^0.5 between
them as shown in Table 1, which is higher than the correlation between the occu-
rrence and solar activity. This may be understood as the consequence of the
favoured condition of ducted propagation for low- latitude whistlers (Hayakawa et
al.,1969; Tanaka and Hayakawa, 1973a, b) . The correlation coefficient between the
solar activity and Cp index is found to be * 0 . 4 , this suggesting a slight de-
pendence of the Cp index on solar activity, as is quite reasonable. However, we
ignore this week correlation between them and we think that the occurrence is
resulted from the combined influence of the Cp index and solar activity as two
independent factors. Now the occurrence is assumed to be expressed by a simple
linear function of the Cp index (Cp) and solar activity (sunspot number, SN) as
follows; the occurrence =3l Cp - 32 SN,and an attempt is made to determine the
constants of 3l and 32 by means of the least square method using the running
means of the above three quantities in Figs. 1,2 and 4, and also to deduce the
correlation coefficients. As the results we obtained the following relation-
ships; the occurrence at Toyokawa-Sakushima = 2.814 Cp -0.010 SN, and the occu-
rrence at Wakkanai-Moshiri = 3.052 Cp - 0.012 SN, and moreover the correla-
D3 - 53
tion coefficients between the occurrence rate observed and that predicted by
the above equations amount to about 0.75. These high correlation coefficients
seem to give us the support to the validity of our assumption that the occurr-
ence rate of whistlers at low latitudes is accounted for by the joint effects
of solar and geomagnetic activities considered to be independent of each other.
The above equations we derived in the present paper will be the experimental
basis of the forecast of occurrence of whistlers.
References
Allcock,G.McK. (1966) : Whistler propagation and geomagnetic activity. J.Inst.
Telecom. Engr s. , 12:158.
Bouriot,M. , M.Tixier, and Y.Corcuff (1976) : Etude de l'ionisation magnetosphe-
rique entre 1,9 et 2,6 rayons geocentriques au moyen des sifflements
radioelectriques recus a Poitiers au cours d'un cycle solaire. Ann.Geo-
phys. , 23:527.
Corcuff,Y., P.Corcuff, and M.Tixier (1966) : Evolution de l'occurrence des si-
fflements radioelectriques entre maximum et minimum d1 active solaire,
C.R. Acad. Sc. Paris, 263:584.
Hayakawa,M., J.Ohtsu, and A.Iwai(1969) : Occurrence and dispersion of whistlers
during magnetically disturbed periods at lower latitudes, Rep . Ionos . Space
Res. Japan, 23:9.
Hayakawa,M., J.Ohtsu, and A.Iwai(1971) : Characteristics of dispersion and occ-
urrence rate of whistlers at low latitudes during one solar cycle, J.
Geomag . Geoe lect . , 23:18.
Hayakawa,M. , and Y.Tanaka(1978) : On the propagation of low- latitude whistlers,
Rev . Geophy s ♦ Space Phys . , 16:111.
Kane, R. P. (1976) : Geomagnetic field variations, Space Sci.Rev. , 18:431.
Kimpara,A. (1962a) : Dispersion of whistlers, Nature, 193:667.
Kimpara,A. (1962b) : Whistlers and solar activity, Nature, 193:667.
Markson,R. (1971) : Consideration regarding solar and lunar modulation of geo-
physical parameters , atmospheric electricity and thunderstorms . Pageoph. ,
84:161.
Tanaka,Y., and M.Hayakawa (1973a) : The effect of geomagnetic disturbances on
duct propagation of low- latitude whistlers. J. Atmos. Terr. Phys. ,35:1699.
Tanaka,Y., and M.Hayakawa (1973b) : Storm-time characteristics of low- latitude
whistlers. Planet. Space Sci. , 21:1797.
D3 - 5h
ATMOSPHERIC RADIO NOISE MEASUREMENTS IN LF/MF BANDS
A. K. Bhatnagar and Mangal Sain
Research Department, All India Radio
Indraprastha Estate, New Delhi 110002, India
1. INTRODUCTION
Noise is an important parameter in the system planning of a broadcasting
service as the minimum signal required for a certain grade of service depends
directly upon the prevailing noise level at any location, in the absence of
any other interference. In most of the tropical countries man-made noise is
low, especially in rural areas, and the atmospheric radio noise which is of
terrestrial origin emerges as the principal source of noise interference in
the LF or other broadcast bands. The extraterrestrial or galactic noise
becomes relevant only at very high frequencies.
In order to assess the acceptable requirement for primary grade sound
broadcasting service in the LF band, the Research Department of AIR has been
conducting atmospheric noise measurements for some time at certain typical
locations in India like Delhi (28°35'N, 77°5'E), Trivandrum (8°29'N, 76°56'E)
and Gauhati (26°N, 91°55'E) .
2. ATMOSPHERIC RADIO NOISE MEASUREMENTS
Measurements of atmospheric radio noise were started at Delhi in 1975
at 155 kHz for a 6 kHz bandwidth, on a long-term basis. To cover some typi-
cal areas, the measurements were started at Trivandrum on 155 kHz, 225 kHz
and 1630 kHz and also at Gauhati on 155 kHz and 525 kHz for a bandwidth of
6 kHz in 1977- Both Trivandrum and Gauhati, which represent southern and
eastern parts of India, are known to have high thunderstorm activity. Stand-
ard field strength meter having charge and discharge time constants of 1 and
600 milliseconds, respectively, have been employed for noise measurements
using a recorder with a response time of ^00 milliseconds. American National
Standard Institute (ANSI) has recommended the use of charge and discharge
time constants of 1 and 600 milliseconds, respectively, for the quasi peak
measurements of atmospheric radio noise (CCIR Report 227-1, 197*0 • On the
basis of experience gained while analyzing the noise records collected at
Delhi and elsewhere it has been realized that charge and discharge time con-
stants of 1 and 600 milliseconds, respectively, give a better and more realis-
tic assessment of impulsive type of noise prevailing in tropical areas when
monitored with the sound program rather than using charge and discharge time
constants of 10 and 600 milliseconds after Thomas and Burgess (19^7), or even
if measurements of noise are taken using the ARN-2 method of CCIR (CCIR
D3 - 55
Report 322-1 and NBS Report 55^5) - Accordingly the noise records at Trivan-
drum, Gauhati and Delhi have been taken using charge and discharge time con-
stants of 1 and 600 milliseconds in 1977-78. Each recording has been taken
for 5 minutes at each frequency during every hour in the time blocks 1200-
1600, 1600-2000 and 2000-2400 hours. A noise recording of 5-minute dura-
tion has been considered sufficient for correct evaluation of noise from the
analysis of noise data.
ANALYSIS OF DATA AND DISCUSSION
Table 1 gives the comparison between the median values of the measured
noise field at 155 kHz during different time blocks and those predicted from
CCIR Report 322-1. It may be observed from Table 1 that in almost all cases
the measured value of noise is less than the predicted one--the difference
ranges from 3 dB to 20 dB considering all the three stations.
Table 1. Comparison between measured and CCIR predicted
median values of atmospheric noise [dB(uv/m)] at 155 kHz
for Delhi, Trivandrum, and Gauhati for 6 kHz bandwidth.
Season Time Block Del hi Tr ivand rum Gauhati
(Hours) M P D(dB) M P D(dB) M P D(dB)
_LM T
1200-lSbO 125 -7 1215 3 £.5 7 0.5"
Winter 1600-2000 16 25 9 13 26 13 9-5 23 13-5
2000^2400 __ 22_3£ £ _ IAi5J2 _ J_5_^5 14 28 I 4
1200-1600 - - - 15 29 14 14 24 10
Spring 1600-2000 - - - 20 37 17 28 35 7
200022400 _ _-_ -_ -_ _29_ _38_ 9_ _3J_. 5 37_ 5.. 5
1200-1600 25 40 15 13 33 20 1 1 ¥o 29 ~
Summer 1600-2000 29 35 6 25 33 8 21 36 15
200022400 3.1 _38 7 _3i _34 _}_ _32_ 4l_ 9
1200-1600 14 28 it 15 29 14
Autumn 1600-2000 22 36 14 22 36 14 -
2000-2400 24 38 14 30 38 8 -
Note: M = Measured P = Predicted D = Difference (P-M)
In order to find the amplitude probability distribution of noise, the
data collected at Delhi, Trivandrum and Gauhati during the different time
blocks has been analyzed. The distribution has been found to be log normal
with a standard deviation of 7 dB .
Satyam(1962) , Laxshmi narayana( 1962) , and other workers have- investigated
the short- and long-term amplitude probability distribution characteristics
of atmospheric radio noise in India. They have found the distribution to be
log normal. For such a distribution Norton has provided a theoretical formula
D3 - 56
to determine the upper decile value of noise if its median value is known.
If the standard deviation is a, the upper decile value (UD) of noise may be
found from the relationship; UD = m + 1.282xo, where m is the median value of
noi se.
It may further be seen from Table 1 that the measured median value of
noise of 32 dB (uv/m) at 6 kHz bandwidth (3^dB at lOKhz bandwidth) has been
observed at Gauhati in summer during 2000-2400 hours. Using Norton's formula,
the upper decile value of the noise is 43 dB (uv/m) at 10 kHz bandwidth.
Upper decile values of noise have also been directly computed from the
recordings made at Delhi, Trivandrum, and Gauhati on high local thunderstorm
activity days during the months of July and August 1978. These values are
given in Table 2. It may be noted from the table that these values range
from 45 dB to 55 dB and that irrespective of the location, the magnitude of
noise intensity is the same. The maximum upper decile value of noise is 55 dB.
Table 2. Measured upper decile values of atmospheric noise [dB(uv/M)J
for localized thunderstorm activity days during July/August at
155 kHz for Delhi, Trivandrum, and Gauhati for 6 kHz bandwidth.
Month Time Block Delhi Trivandrum Gauhati
Hours
(LMT)
July
1200-1600
45
and
1600-2000
48
August
2000-2400
50
45 48
50 53
52 55
COMPARISON OF NOISE IN THE LF AND MF BANDS
As stated previously, the atmospheric radio recordings have been made
at 155, 225/235, 525 and 1630 kHz at different locations in India. From
these recordings the median values of noise have been worked out at each
frequency. These values have been normalized for 200 kHz and 1 MHz in the LF
and MF bands, respectively, knowing the values of noise at the lower and
upper ends of each of these bands. The median values of the measured noise
and those predicted from CCIR Report 322-1 are shown in Table 3 for both
bands. It may be observed from the table that the CCIR predicted values of
noise are mostly greater than the measured ones and generally the differences
are quite large, amounting to 18.5 dB. From this analysis it is evident that
CCIR Report 322-1, needs to be revised.
D3 - 57
Table 3- Comparison between measured and CC I R predicted median values
of atmospheric noise (dB) at 200 kHz and 1 MHz for Delhi, Trivandrum,
and Gauhati for 6 kHz bandwidth.
Place Season
Time Block
Hours
(LMT)
200 kHz
1
MHZ
M
P
D(dB)
M
P
D(dB)
Delhi
1200-1600
34
37.3
+3.3
17.8
12.3
-5.5
Summer
1600-2000
32.3
33.3
+1 .0
16.9
14.3
-2.6
2000-21*00
36.8
34.3
-2.5
22.6
19.3
-3-3
1200-1^00
3*-
11.3
1.9
-
-
-
Winter
1600-2000
11
24.3
13.3
2.4
9.3
+6.9
2000-2*t00
16.4
30.3
13-9
6.2
16.3
10.1
1200-1600
13
24.3
11.3
_
_
-
Spri ng
1600-2000
18
30.3
12.3
8.2
14.3
6.1
2000-2400
25
33.3
8.3
11.7
20.3
8.6
Trivandrum
1200-1600
10.0
30.3
20.3
3.8
4.3
0.5
Summer
1600-2000
16.4
28.3
11.9
6.3
15.3
9.0
2000-2400
27
32.3
5.3
14.0
17.3
3-3
1200-1600
12
26.3
14.3
0.8
0.3
-0.5
Autumn
1600-2000
18.4
31.3
12.9
7.2
14.3
7.1
2000-2400
24.4
33.3
8.9
12.2
20.3
8.1
1200-l"6~00
5."6"~
8.3
2.7
-
-
-
Winter
1600-2000
8.8
16.3
7.5
0
4.3
4.3
2000-2400
13
25.3
12.3
1.9
10.3
8.4
Gauhati
1200-1600
11.6
19.3
7.7
-
-
-
Spring
1600-2000
26
31.3
5.3
11.3
12.3
1.0
2000-2400
30
33.3
3.3
20.3
20.3
0.0
1200-1600
_
_
-
4.8
11.3
6.5
Summer
1600-2000
18.8
33.3
14.5
9.8
14.3
4.5
2000-2^00
29.8
37.3
7.5
19-8
22.3
2.5
Note: M = Measured P = Predicted D = Difference (P-M)
5. CONCLUSION
The following conclusions can be drawn:
1. The measured median values of atmospheric radio noise in the LF
and MF bands for the three typical locations (Delhi, Trivandrum and Gauhati)
in India representing different typical thunderstorm activity regions, have
always been found to be lower than those predicted from CC I R Report 322-1.
As such the report needs revision.
2. The amplitude probability distribution of noise has been found to be
log normal .
D3 - 58
3. During high local thunderstorm activity days the upper decile value
of atmospheric radio noise for three different locations in India has been
found to range between **5 and 55 dB.
REFERENCES
CCIR Report 227-1, General methods of measuring the field strength and
related parameters, Vol ume V (197*0, Published by ITU, Geneva.
CCIR Report 322-1, World distribution and characteristics of atmospheric
radio noise, Published by the ITU, Geneva.
NBS Report 55^5, Instruction book for ARN-2 radio noise recorder, Published
by N.B.S, Boulder, Colorado.
Norton, K. A.; Voglar, L. E.; Mansfield, W. V. and Short, P. J. (1955): The
probability distribution of the amplitude of a constant vector plus a
Raleigh distributed vector, Proc. I.R.E., hi , p. 1354-1361.
Satyam, M. (1962): Short term amplitude probability distribution of impul-
sive atmospheric radio noise, J . S . I . R . (India) , 21D, 221-227.
Laxshminarayana, K. M. (1962): Short term time characteristics of impulsive
atmospheric noise, J.S. I ,R. (India) , 21D, 228-232.
Thomas, H. A. and Burgess, R. E. (19^7): Survey of existing information and
data on radio noise over the frequency range 1 - 30 MC/S, Radio Research
Special Report No. 15, H. M.'s Stationary Office, London.
D3 - 59
PREDICTION OF WAVEGUIDE PROPAGATION OF RADIO WAVES
USING THE EXTREMAL-PARAMETRIC METHOD BASED ON
PREDICTED IONOSPHERIC PARAMETERS
A. G. Shi ionsky
Institute for Terrestrial Magnetism, Ionosphere and
Radio Wave Propagation of the USSR Academy of Sciences
1^2092, Troitsk, Moscow Region, USSR
The concepts and the basic expressions of the mathematical
formulation of the extremal -parametr ic method (EPM) for calculating
the characteristics of radio waveguides is presented. EPM has been
based on the analytical dependencies of the channel character istiics
on the extrema of the modified refractive index and the latter's
dependence on the extrema of the vertical gradient of electron
density. In this case, predictions of the key ionospheric param-
eters (critical frequencies, geometric parameters, and the param-
eters of N,L and interlayer valley) may be used to predict the
waveguide characteristics.
After establishing the fact that radio waves may be rebounded in iono-
spheric waveguides (Krasnushkin , 19**7), the theoretical studies have been di-
rected toward a quantitative analysis including the variations of the real
ionosphere. Several methods of calculation are possible, depending on the
mathematical formulation, the physical factors included, the ionospheric data,
the ionospheric models used, the determinable characteristics, etc. It is
most important to analyze the experimental data obtained from long- and very
long-distance link lines, in order to design a theoretical model that is a
comparatively simple mathematical formulation. This should be combined with
sufficiently accurate ionospheric models and available ionospheric data.
Presented below are some results of the systematic generalization of the
formulation of the extremal -parametr ic method (EPM) for calculating iono-
spheric waveguides. Also presented are the analytical dependencies for some
integral characteristics of the channels. The material set forth below sup-
plements earlier works (Shi ionsky, 1965-1977) that presented the concepts
and a number of expressions for EPM.
The formulation for EPM consists of three basic sets of expressions:
1. the differential conditions for the extrema and the knee point
U(r) = r2n2(r) (where r is the geocentric distance and n is the refractive
index) and for the limiting case of degeneration of theU(r) nonmonoton ism
and disappearance of the channel;
2. the analytical dependency of the parameters of the extrema [U(r)]'r
D3 ~ 60
on the parameters of the extrema [f ^ ( r ) ] ' r and on the working frequencies as
obtained from the combined quadratic model f^Cr), where f|g is the plasma fre-
quency of the ionosphere;
3. the analytical dependency of the various characteristics of the
channels (integral, etc.) on the parameters of the extrema [u(r)]'r and
V = Ugsin2 <f>o (<J> is the angle between the ray and the vertical; the subscript
"0" denotes the initial conditions) obtained from the combined quadratic
model L)(r) .
The first set of EPM expressions will be written in the general form of
the geometric-optical approximation as
n2+I (n2); = 0 (1)
n2+ 2r(n2)p + £- (n2)- = 0 (2)
(„2). + r (n2)n = 0 (3)
Here, condition (1) corresponds to U' = 0 for the extrema U(r); condi-
tion (2) corresponds to Up = 0 at the U(r) knee point; and condition (3)
corresponds to the simultaneous satisfaction of conditions (1) and (2) at the
level of the L)(r) nonmonotonism degeneration.
The equivalent set of expressions for n2 = 1 - f^|/f2 (i.e., disregarding
the effect of the magnetic field, H, and of the number of charged particle
collisions, v, on the refractive index) is of the form
f2N(r) +£ [f2(r)]; - f2 = 0 (k)
[fN(r)]r *TIfM(p)1; ~b[f2 - fN(r)] =0 (5)
[f2N(r)]r + j [f*(r>]» = 0 (6)
The condition equivalent to equation (2) may also be presented as
(Shlionsky, 1971):
2
[f5(r)]:»i[f£<r)l"»f-ftlfeUftsii °0 (7)
W'r + 2 LrN*r'Jr + TTTf? - fft(r)]
Condition (M has been used to obtain the following expressions for the max-
imum operating frequencies of rotation of the rays emitted horizontally from
the initial level r and, in the extremum, from the degeneration level rj
satisfying condition (3) (Shlionsky, 1965 and 1971).
fma*<r> ' /f^)^t^(r)]/ (8)
fmax ■ /w'+piwn (9)
It follows from condition (7) that r, > r [the indices k and g correspond to
the knee levels U(r) and f?.(r)] since the"third term is positive and the
first and second terms should be of different signs in the upper vicinity of
rg. It follows from condition (6) that rj > rg since the signs of the first
D3 - 61
and second terms should be of different signs in the upper vicinity of r .
The shift, rj - rq , may be obtained from condition (6) as
rd " rq / rf2N(r)]r=rg \ ^ , x
— 2- = / 1 .2 9- -V+0.04 -0.2 (10)
g
A second set of EPM analytical expressions has been obtained (Shi ionsky,
1965-197^) from condition (k) using the combined quadratic model, fKi(r), sat-
isfying the following basic requirements:
for the extrema, [fN(r)]' = 0
[f?,(r)]H > 0 below r
N r g
[f^(r)]»; < 0 above rg
A sector of a parabola with vertex at the level r F will be used above
., , . K max
the r 1 evel :
9
f|(r).f§ [i - (rMV r)2 1
ym
Since the level rj of channel degeneration is shifted above the level rq,
the upper boundaries r^ of the channels are above rq in the altitude region
approximated by this model. The channel axes, rg. Tie in the altitude region
limited from below by r^, the minimum level of fi. in the valley. In this
altitude region, fN(r) is approximated by an inverted parabola with a vertex
at the r 1 evel :
y
P- £*- D2/(l - fyf2)
rM / N q
_M 1 n g
The second set of EPM expressions is of the form
r /2
-A- = 0.75 + 0.25 {i - 8 4s— t(f/f0)2 - 1]}55 do
r .. rm 3v
max
max
^_= <^)2 {, . In - (^x)2(, --^)2]> (12)
rmax rmax T ym rmax
D3 - 62
2
/= 0.75 + 0.25 {1 + 8p [|- + -^]}i5 (13)
7* = ^ {1 " « [("T)2 + 77 ^ " 1)2]} (1/t)
rR rM f2 fg P rM
The set may also include the expressions
r. - r and U. - r2(l - ■#)
kg k g fz
As the difference r^-r (and hence r^-r _) is usually small, r^ may ap-
proximately (with some underestimation) be taken as rq . Some characteristics
are functions of the key parameters f».(r). Substituting the conventional
parabola in equation (8) we get
Isssil-O + (I=Si)2 [S-E-- 2 (-L_ )2 - ,]>* (15)
0 ym max rmax
Consider now the third set of analytical expressions for the character-
istics of the ionospheric channels. It is expedient to distinguish in the
third set the small group of nonintegral characteristics (transverse alti-
tudes of the channels, refraction-angle characteristics of radiowaves when
they are trapped in and escape from the channel, etc.) that can be presented
directly as functions of the V and U(r) extremum parameters. The limiting
transverse altitude of the channel is
A r < rA - /07
where /LJ^ = rcn(rc) and rc is the lower boundary of the channel; rc > AT£
since n(rc) <, 1. The transverse altitudes of the channels corresponding to
the low-sloping rays (reflected below r ) are
(■"k - rB) (rB - rM)
VuB - uk' vAJb - um'
Ar = /0^T [^L^ + ^L^]
The angles necessary for turning the rays trapped in a channel are
A<b . = arc sin/ n"~ - arc sin/ 77— {\b)
mm UB UB
when the emitter is on the channel axis (Shlionsky, 1 97^c) , and
Ad> = arc cos/ 77— (17)
max U.
when the emitter is at the channel boundary, and
D3 - 63
/V / «v
A<J> = arc cos/tj— (18)
UB
when the rays glide along the channel axis.
When the absorption coefficient, Y, is a minimum for ionospheric ducting
along the axis rg, i.e.,
3f v(rB(f)) =0
(the collision frequency is nearly constant in the channel), we obtain an ex-
pression for the optimal frequency, fODt (Shi ionsky, 1977):
f~l?1= {1 + [(fn/fM> - ^/Kr /rM) - )]2}h (19)
• M g M / g M
The majority of the EPM expressions of the third set correspond to the
set of the integral characteristics of ionospheric channels. For these, the
analytical expressions can be determined from a combined quadratic model L)(r)
(Shi ionsky, 197*0, which makes it possible to tabulate the corresponding in-
tegral s
e = vYf" dr - £L= L - l
rVu(r) - V* V 9 P
u , A y ,
L = / rdr T - / /U(r) - Ufl dr
9 /U(r) - V j A
r r
L = f" U(r)dr j Mr) _ v.dr
P r/u(r) - V
where 0 is the interval of ray oscillations in the channel; l_g and Lp are the
group and phase path; r is the absorption, T is the limiting volume of the
channel in its given cross section; and To . is the adiabatic invariant or the
initial volume of the channel for the ray (Gurevich, 1971) .
The integrals are reduced to a tabular form using the combined quadratic
model U(r). In this case, the U(r) dependence above and below r^ can be ap-
proximated by the various quadratic models that satisfy the following main
requirements: Up = 0 in the extrema; U(r) and Ur' > 0 above r^; and U'r' < 0
below r^.
We use the model (Shi ionsky, 197^a)
"<r> ■ ub - % - v (i[ : $
in the altitude region rR, r. and the model
2
in the altitude range r, , r . The corresponding expressions for the levels
D3 - 64
of the upper points of the turn are obtained from the condition U(r) - V = 0.
t wUB ~ V sh
ru = rB + (rk - rB)(u— n^}
V - UA \
ru = rA - (rA - rk)(Uk - uA)2
The combined quadratic model U(r) is equivalent to the combined quasi-
parabolic model fjjUr).
In fact, we have from the equality
fK,(r) (rA - r)2
U(r) = r2[l - -^-] = UA + (Uk - UA)(pA _ r )2 (for r > rk)
f5(r). ... >A - r)
'A ' rk
that
:2
A (uR - UA) (rA - r)2
fg(r) = f (1 - [w + 3 ( _ )2]}
A
In this case, the level rA(f) is the upper limit of the altitude region fjg(r)
for a given f.
The characteristics of the rays reflected below rk (low-sloping rays)
are determined from only the first model of U(r) by integrating from rg to r^
The characteristics of the rays reflected above r^ (steep rays) are de-
termined from both models of U(r) by presenting the integral as the sum of
two integrals in the corresponding altitude regions, i.e., rg, rk and rk, ru.
Presented below are the analytical dependencies obtained for some in-
tegral characteristics.
The expressions for the characteristics of the low-sloping rays (V > Uk,
ru < ry) are of the form
0 = / -4 r arc cos/ B (20)
2
1 - VUB o V
al = ~T, 2 ; gR = M SIP
(Us - l) B
rB
, ^B(rk - rg) (rk - rg^/Ug^/
9 = ~2 ^i^r + (ub - u^
[ 1 [UB.^B-Uk)r§ ^ rB/ UB - Uk (UB - Uk)
P /7 B <rk " rB)2 (rk - rB) (rk - rB)2 g
cr ,, , <»B - "!>) , , (»B - Vr8 „ ,'/V'k
B; v'k "B
r?k - rB)^JLg " ^lUB " (r, - rD)2 ° (r, - rD) (23)
D3 - 65
T° = k
* (rk ^ re) /uT^T
/ UD - Ui,"
'B
(24)
'B
Equations (22) and (23) show the determined link between the integral char-
acteristics. They are the relatively invariant initial conditions of
emission, V.
The expressions for the characteristics of the steep rays (V < Uk,
rM > rv) are of the form /
""A to UAx
■g- a - (B - tH
rk Uk
-i *n
/rA (1 - 3) 1 - a' +^V
/ 9 II.
rA/l -
Ha
r? , UAv a
rK (B - -A)
uk
r/7T^
UA 1
u.
^
arc s in
^7
S*i + B
/cTJ + BB - 1'
. /! - Br
=i arC Sin r— , " ;
- 1 /of
/(i . ^B) ^r ^tb - 1 )
. •oT' — / 1 - BR' —
rB B rB
(25)
-■a -£>/#.„■
= u7= s,n \
k
L E
g
<rk - rB^ t/V^- ^V^] ^^ (rA " rkF
(uB " uk)
(Uk " V
(ri, ~ rR)
rBvrk " rB'
+ — arc sin
/UB " Uk'
in[
A^
/uB - Uk rA<rA - rk>
/uB - v" / uk - uA Vuk - uA' - /uk - V
L =
P
(UB - Uk)rB2
B K " rB)2
/(Ur - Uk)rT~ In w\
/ (rk - rB^ " (UB " V)
— { arc s in
(26)
(UB - V)(rk- rB) + (UB - Uk)rB
rk/UB " U. /UB - V"
. /UB - V'(rk - rB} rB K - Uk . /UB - Uk
- arc sin } + arc sin — ,. ,- +
rB/UB - Uk'
(rk " rB}
\ ' V"
D3 - 66
ru + '"k ' V^, /W 177 .AT— 7 . (VUA)rA (v u ,
+ - , in
[r ]
V uk - u ■ / uk - u' - / u - V
(rA ~ V / V - UA B
(r. - rj , , , / UR-U '
/UB " Uk ^ UB_UA
+ I^A-^/Vr^ (28)
(r. - r ) . /UB - U "
T0= k B 1 [• UR - u/ ru—--\P + (UR - V) arc sir/ B k ]
r^-nrk 2 b k k b /TJ-rirA
(r -r )
+ j , A , {(V-UA) ^nvHRJ^+Z Uk-UA/ Uk-V - (V-UA) An (• Uk"UA +/u~^/)>
•fyc"UA
(29)
The above expressions for 0(<{>o) and the U(r) are used to obtain the
analytical dependence of the electric field in the waveguides.
The longitudinal focusing of the ray's energy in the propagation plane
can be expressed in the general form by the factor (Rawer, 1952)
sin <j>0/[cos <J>(r) ■ dO(<t>0)/d<}>0] . (30)
Considering L)(r) sin2 <J> = U(r0) sin2 <J>q , we get
s!n *o = ] , , t (3D
cos ♦(r) /esc2 <fr0 - ^T~
where U(r) for any level r can be found using the quadratic model for a given
altitude region:
D3 - 67
U(r) = r2 at levels below 100 km, where n * 1
U(r) = a2 at the Earth's surface (a is the radius)
U(r) = U(ro) at r = rg • In this case
sin 4>0/cos (j>(r) = t d>0 (32)
The analytical dependence for sin <J>o/cos $(r) may be obtained by com-
bining the U(r) models for various regions corresponding to the altitudes of
the emitter and receiver.
Differentiating the expressions for 0 (<j>0 ) over <J>o , we get for the low-
sloping rays:
d©(<J>o) sin2 An (1 - ai) cos <j>n rcos d>m /-,-,\
,. w = 7 •) 1 \ " 1 x 7 I \H/7- arc cos [ > Y'J (33)
d<j>0 (a! - cosz (j)0) (ax - cosz <$>o) ' Voi
The low-sloping rays are most important since, as $q becomes lower, the
probability of the ray retention in a channel decreases over a considerable
length of the channel:
173/ P(4>o)'
E(r.e) = , ,/jy r-^ (3*0
/ sin 0 r/cosec <|>0 - H/'V /d0(4>o)/dcj>o
where P is the radiated power; E is the field intensity.
The factor l//sin 0' includes the ray beam divergence at 0 < 0 < tt/2 and
the subsequent convergence (focusing) up to the antipode at (u/2) < 0 < ir in
the direction of the propagation plane due to the sphericity of the medium.
By representing U(ro), U(r), and d0(<j>o)/d<f>o corresponding to the various
altitudes of emitter and receiver and the ranges of ejection angles, <f>o , we
obtain a series of analytical expressions for E(r,0).
It follows from the EPM dependencies obtained that the max Nr and the
valley parameters are of great importance when forming the qualitative pattern
of radio wave propagation and can significantly affect the majority of the
channel characteristics.
For example, the limiting maximum frequencies of waveguides fmax are
direct functions of the max Nr parameters.
Figures 1 and 2 present the diurnal variations in fmax and fmax/foF2
calculated for medium-latitude models for winter, low solar activity W(a) ;
summer, low and temperate W(b,c). The fmax/f°F2 ratio varies between 5 and
10, i.e., 2 to 4 times MUF/foF2. The highest values are reached at night.
The amplitude of the diurnal variation in summer is much larger than in win-
ter. The absolute values of fmax vary within 20-60 MHz and increase with W.
The EPM formulas have been used to calculate the intervals of the ray
oscillations, 0 (<}>o ) • ' n tne general case, 0(<J>o) is a nonmonotonic function
with a high peak corresponding to the limiting steepest ray, an intermediate
minimum for the ray reflected near rq, and a weak second peak for the lowest-
sloping gl idi ng ray.
The rays reflected near the rq level correspond with the maximum of the
group part and with its decrease towards steeper and lower-sloping rays.
The max N^. parameters also affect significantly the field distribution
in a channel. As the angle, $q , increases when the ray approaches the channel
axis, the focusing increases monotonical ly , whereas the absolute value of the
field for a fixed $q (depending on the parameters of the medium) increases
D3 - 68
5 S 7 1 11 «5 iS </ *i 2i iS^T
i5 «5 *T «i .< 23 if
Figure 1. Diurnal variations in f
max
Figure 2. Diurnal variations in
with increasing 04 ■+ 1 . For the extremely low-sloping rays reflected near rg,
sin <f>o is significantly smaller than on the channel axis, although dO/d<t>o ex-
hibits a minimum. Therefore, the focusing is not as great.
At the upper boundary of the channel r«, the field reaches its zero
value since dO(<t>o)/d<j>o = °° for the extremely steep ray. The field maximum is
located near the channel axis and corresponds to a gliding angle with <J>q = tt/2
and dQ/d^Q is small. The valley parameters affect directly the channel axis
position, rg, and Ug and all the characteristics depending on rg and Ug.
Thus, the mathematical formulation of EPM consists of a set of expres-
sions which, in combination, give the analytical dependencies of the various
channel characteristics on the key parameters dN/dr. In other words, the
available global predictions of critical frequencies, the geometric parameters
of ionospheric levels, and the data for the parameters of the dN/dr maximum
and the interlayer F/E valley may be used to determine EPM.
D3 - 69
REFERENCES
Gurevich, A. V. (1971): Effect of nonlinearity on generation of round-the-
world signals, Geomagn. i Aeron. , 11:961-969.
Krasnushkin, P. E. (19^7): Method of normal waves as applied to the problem
of long-distance radio communication, Moscow State University, Moscow.
Rawer, K. (1952): Calculation of sky-wave field strength. Wireless Engineer,
29:287-300.
Shi ionsky, A. G. (1965a): Some remarks concerning the ray methods of calcu-
lating the radio communication on short waves, Geomagn. i Aeron. ,
5:1052-1060.
Shi ionsky, A. G. (1965b): Damping of satellite emissions for near-ground
trajectories, Geomagn. i Aeron. , 5:1061-1067.
Shi ionsky, A. G. (1970): Dependence of the position of the rn(r) -function
maximum on the altitude profile of ionization in "valley" and on the
operating frequency, Geomagn. i Aeron. , 10:1^7-1^8.
Shi ionsky, A. G. (1971): About reflecting MUF of radio wave at over-Earth
ionosphere wave propagation. Preprint No. 12, Moscow, IZMIRAN.
Shi ionsky, A. G. (I97^a): Some trajectory characteristics of radio wave
ducting in the ionosphere. Collection IZMIRAN, The Questions of Short
Radio Wave Propagation, part 2, 77-87-
Shi ionsky, A. G. (197^+b): The variations rn(r) -function maximum of the
ionosphere. Collection IZMIRAN, The Questions of Short Radio Wave
Propagation, part 2, 88-94.
Shi ionsky, A. G. (I97^c): The refractive characteristics of the seizure and
going out from the ionospheric waveguide. Collection IZMIRAN, The
Questions of Short Radio Wave Propagation, part 2, 95-100.
Shi ionsky, A. G. (1977): The frequency dependence of the radio wave
absorption in ionospheric channels. Collection, The Methods of the
Research of Regularities in Radio Wave Propagation, Moscow, Nauka, k5-k3.
Shi ionsky, A. G. ( 1 968) : Determination of the extremum levels of the rn(r)-
function and MUF under various ionospheric conditions, Geomagn. ?
Aeron. , 8:367~368.
D3 - 70
E. SATELLITE AND ELECTRIC POWER APPLICATIONS
ANOMALOUS SATELLITE DRAG AND THE GREEN-LINE CORONA
Richard C. Altrock
Air Force Geophysics Laboratory
Sacramento Peak Observatory-'-'
Sunspot, New Mexico 883^9
Satellite drag data for Skylab from Headquarters Aerospace
Defense Command are compared with solar X5303A Fe XIV coronal
scans from Sacramento Peak Observatory. During a short period
in late 1977 and early 1978 there appears to be a distinct anti-
correlation of anomalous drag with coronal intensity inferred
at the center of the solar disk approximately two days earlier.
The relation appeared at a time of a stable intensity pattern
near the solar equator and evidently disappeared as the stable
intensity pattern disappeared.
NTRODUCTION
It has been well established that coronal holes as observed in X-rays
are the source of high-speed solar-wind streams. A number of studies have
shown that streams emanating from holes near the sub-earth point impact on
the geomagnetic field and cause disturbances in it (cf. Neupert and Pizzo,
197^)- More recently, studies have shown that coronal holes may be iden-
tified in observations of A5303A of Fe XIV with sufficient precision to
allow use of these data to predict recurrent geomagnetic disturbances dur-
ing times of low solar activity (cf. Musman and Altrock, 1978). However,
at best this technique results in a success ratio of approximately 80%.
There are, therefore, times when an apparent low coronal emission at the
sub-earth point does not result in a geomagnetic disturbance. This
apparent lack of 100% correlation between regions of low emission in the
green-line corona and high-speed streams has been confirmed by Kaufman
(1978). This paper explores further the properties of these low-emission
regions in their effect on another geophysical parameter.
* Operated by the Association of Universities for Research in Astronomy,
Inc., under contract with the National Science Foundation
E - 1
Recent Studies of satellite drag produced by density fluctuations in
the atmosphere have, resul ted in inference of an anomalous drag that is
uncorrelated with, among other parameters, geomagnetic disturbances (Lane
and Hoots, 1978). Following a request from Headquarters Aerospace Defense
Command, a preliminary comparison of these data with green-line data
showed a favorable correlation with regions of low emissivity, and I have
now found a subset of the observations that implies a direct connection
between stable regions of low green-line emissivity and increases in ?
satel 1 i te drag.
THE DATA
The observation and reduction of the green-line data are described in
Musman and Altrock (1978). The data are basically coronal intensities at
a given height above the limb obtained daily. I have utilized an equatorial
average of the intensity in the .latitude band +15 to -15 •
The satellite drag data are presented in the form of the total drag
coefficient, B, having units of m2/kg. The total drag is defined to be
pB, where p is density taken from the Jacchia 1964 model, which includes
empirical corrections for geomagnetic index, a , and solar radio flux at
10.7 cm, FjQ.7- Data are presented for Skylab (other data are being
processed). The value of B is determined by comparison of the modelled
motion with radar observations. Thus, variations in B represent un-
modelled, or anomalous, variations in total drag.
The data are presented in Figure 1. The data set of B corresponding
to unstabilized motion of Skylab ran from approximately DOY 3^0, 1977, to
DOY 160,_1978. Data gaps of one day in I have been linearly interpolated
over. I has been plotted increasing downwards.
RESULTS
Referring to Figure 1, we see that a stable coronal intensity pattern
with a period of 27 days existed near the solar equator near the end of
1977- The intensity data became rather sketchy near the beginning of 1978,
but at least four maxima can be inferred in this pattern (DOY 31^, 3^1, 5,
and 31). A fifth possible maximum near DOY 60 cannot be confirmed. After
that, the intensity pattern can only be described as chaotic, with consider-
able difference between disk-center intensities inferred from east and
west limbs and no clear recurrent features.
The satellite-drag data show many similarities to the shifted intensity
values in the first half of the observation period. With an empirical
value for the shift (or transit time from the center of the disk) of
E - 2
2 5
A^Av
\ /J ** \ /
v -^
Figure 1: Total satellite drag coefficient for Skylab, B, (solid line)
and average coronal A5303& intensity, T, (dashed lines) as a function
of day of the year at the earth, DOY^. Uncertainty bar near B represents
the integration time of each point. The 30 latitude average of
equatorial green-line intensity is plotted at the day of limb passage
(LP) + 8.75 days for east-limb data and at LP-4. 75 for west-limb data,
or at CMP + 2 for either limb. No distinction is made on the graph
between east and west limb data. Circles represent isolated data
points of I .
approximately two days, the maxima in I correspond well to the minima in
B (DOY * 342, 35/t"359, and 29). Other data, unavailable for publication
at this time, show a similar pattern. The maxima in B at DOY ^ 3^6 and 13
(and 37-^0?) have associated minima in I. As time progresses, the station-
ary pattern in the corona become? chaotic, and no clear periodic signal is
seen in the B curve. Another interesting feature in B is the decline in
the average level, beginning about DOY 60 and bottoming out near DOY 117-
This does not appear to be correlated with any particular event in the
equatorial corona, although it does correspond, more or less, to the onset
of the chaotic coronal intensity pattern.
The choice of a transit time (shift) of two days from CMP is arbitrary
and uncertain. Digital data was unavailable at the time of writing, so a
cross correlation was not performed. A transit time of zero (or 27 days)
actually appears to fit this extremely limited data set better. Alter-
natively, a transit time of eleven days would align the maxima of I with
the maxima of B. This transit time seems unlikely due to the low propa-
gation velocity required {y 160 km s~') and the low probability that such
a slow stream could maintain its coherence over that length of time. One
might expect that such a stream would be disrupted by overtaking high-
speed streams. However, one cannot completely discount the possibility
that the periodic variation in B is due to low-speed streams emanating
from regions bright in the green-line. Because a mechanism for this has
not been identified, I prefer to conclude that the source of the increases
in B lies in faint green-line regions; i.e., a (weak?) high-speed stream.
E - 3
CONCLUSIONS
1. A clear 27~day period has been identified in a portion of total drag
data for Skylab, after correction for geomagnetic disturbances and solar
radio flux.
2. A good correlation of the periodic maxima in this anomalous drag has
been found with a stable periodic low- intensity region in the equatorial
corona as observed in A5303A Fe XIV.
3. The onset of unstable, rapidly-evolving conditions in the equatorial
corona appears to coincide with the disappearance of periodic variations
in corrected drag.
k. From these limited data, it appears that stable regions of low coronal
intensity observed near the equator on the east limb may be used to
predict anomalous increases in satellite drag up to nine days in advance.
ACKNOWLEDGEMENTS
I wish to thank Max Lane and Felix Hoots of the Office of Astrodynamic
Applications, Headquarters Aerospace Defense Command, for supplying me with
the satellite drag data and encouraging me to analyze it.
REFERENCES
Kaufman, J. J. (1978): The latitudinal structure of solar wind streams from
radio scintillation observations, report No. 1, AFGL-TR-78-OI 69, Air
Force Geophysics Laboratory.
Lane, M. , and F. Hoots (1978): private communication.
Musman, S., and R. Altrock (1978): Recurrent geomagnetic disturbances and
coronal holes as observed in Fe XIV X5303A, J^. Geophys. Res. , in press.
Neupert, W. M., and V. Pizzo (197*0: Solar coronal holes as sources of
recurrent geomagnetic disturbances, J_. Geophys. Res. 79:3701.
E - A
EFFECTS OF MAGNETOSPHERIC DISTURBANCES ON THE GEOELECTRIC FIELD IN AURORAL
AND SUB-AURORAL REGIONS, AND INTERACTIONS WITH HV -DC/AC ELECTRIC POWER LINES
LaAgz-6calz man-made. zfi&zctA on thz global aztionomiz znviAonmznt.
Wolfgang-M. Boerner ' \ James B. Cole( \ William R. Goddard(
(1) Communications Laboratory, SEL-1104, UICC, P.O.Box 4348, Chicago, IL 60680;
(2)AEM Laboratory, New Eng.Bldg., Univ. of Manitoba, Winnipeg, Canada R3T 2N2 .
A bai>iz itady ti> ph.opoi>zd to advance. fizi>zaAck on kou) and to what ex-
tznt g zo -magnetic. diituAbanceA a^zct the. gzo-zlzztAic. {ajlIA in au-
Konal, 6ub-auAoial, and zznt/ial latitudinal fizgionA, and to OA4Z66
thziA inteAaztion toith tkz zlzoXAiz ^izlcU, and l/LF noti>z hjadiatzd
^nom HV-AC/VC poweA lineA and otheA man-made, iyitemi.
1. INTRODUCTION
Until fairly recently the studies of geoelectricity and geomagnetism were
largely separate endeavors; and except for highly localized effects of limited
magnitude, man-made systems were thought to have no effect on the macro-geo-
electromagnetic environment. It is now becoming apparent that not only are
geomagnetic and geoelectric fluctuations intimately linked, but that they can
interact with radiations from man-made systems (K.Bullough et al,1976). Al-
though the total energy in atmospheric electrical disturbances is small vis-a-
vis other geophysical parameters (it amounts to about 0.1% of the total kinet-
ic energy of the atmosphere - H. Volland,1979) , evidence is accumulating that
they affect the weather. Helliwell et al (1977) and Park et al (1978) have
presented evidence that relatively weak radiations from electrical power sys-
tems can be amplified by various natural mechanisms, especially in geoelectro-
magnetically active regions, and manifest themselves in effects on the magne-
tosphere thousands of kilometers away fron their origin. The existence of
this effect has been established clearly, yet its relative importance in in-
fluencing the electron distribution in the radiation belts was questioned in
(Thorne and Tsurutani, 1979) and requires further investigation.
The existence of such effects and the possibility of others emphasizes
the need to preface extension of man-made systems such as HV -DC/AC power and
oil/gas pipelines into geoelectromagnetically active regions with careful
investigation.
rr
2. RELEVANT BASICS ON GEOELECTRICITY AND "LUFTELEKTRIZITAT"
In the "classical" theory of geoelectricity, the terrestrial surface and —
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The observotions on the Maud refer
to the Northern Winter only.
Arctic Ocean (Maud)_
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Fig. 2b
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Fig. 2a Diurnal variation of potential gradient over oceans (Chalmers, 1967
p. 164).
Fig. 2b Diurnal variation of potential gradient at Kew, winter and summer
(Chalmers, 1967, p. 162).
Fig. 2c Gegenuberstellung von Sonnenf leckenrelativzahlen und luftelektri-
scher Feldstarke an 5 Landstationeh (Muhleisen,1969, p. 130).
the ionosphere are treated as ideal conductors between which there exists a
potential difference of some 250 kV, the earth bearing negative charge. This
potential gives rise to a vertical electric field at the earth's surface of
approximately 130 V/m. The air is a leaky dielectric filling between the
plates of this giant capacitor, passing a downward positive current estimated
at between 600 and 1800 AMP (Chalmers, 1967 ;Muhleisen, 1971) . Computing the
total charge on earth from its measured surface electric field gives about
450,000 Coulombs (Fleming, 1949) . Clearly in the absence of some charging
mechanism the earth-ionosphere capacitor would discharge within a few hours.
According to the pioneering theory of C.T.R. Wilson (1909) thunderstorms are
continuously at work - some 100 lightning flashes per second - pumping nega-
tive charge down to earth which leaks back to the ionosphere through fair-
weather regions (Fig.l).
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DAYS BEFORE AND AFTER SOLAR FLARES
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Fig. 3 Days before and after solar flares (Roble and Hays, p. 56).
This simple model however is not adequate to explain the dynamic nature
of geoelectricity. The earth- ionosphere current and potential difference ex-
hibit multi-cyclic behaviour with periods ranging from duirnal upwards through
seasonal to eleven years, in apparent correlation with the sun-spot cycle
(Fischer and Muhleisen, 1972 :Figs. 2a,b, c) ; correlations are also observed with
such events as solar flares (Reiter,1972 :Fig.3) and the earth's passage across
solar magnetic sector boundaries - where the sun's magnetic field changes from
inwardly - to outwardly - directed (Reiter, 1976; Herman and Goldberg, 1978 :Figs.
4,5). Thunderstorm activity has also been observed to correlate with solar
magnetic boundary crossings (Lethbridge, 1978) . Localized variations in the
atmospheric electric field and current density also occur which depend upon
topography, meteorological conditions and local time. These can mostly be
accounted for as arising from local variations in atmospheric conductivity in
response to changes in ion production and dissipation rates (Israel, 1969) . On
a shorter time scale and localized to auroral and near-auroral regions, dra-
matic geoelectric fluctuations including field polarity reversals are recorded
in association with auroral activity (Olson, 1971 :Fig. 6) and during geomagnetic
storms (Lanzerotti,1977) .
Observed correlations between solar events and fluctuations in atmospher-
ic electrical parameters on the one hand and the theoretical link between
atmospheric electricity and thunderstorms on the other might tempt one to
postulate some relationship between solar events and terrestrial weatner. In
fact hundreds of statistical correlations have been found between solar acti-
vity and weather - mainly rainfall and atmospheric vorticity (Herman and Gold-
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Time (GMT) Olson , 1 9 71 , P. 129
Fig . 6 . Electric field and magnetometer measurements during an AEAE on 4 September 1966 GMT, Duluth,
Fort Churchill, Great Whale River, and Fredericksburg (38.2°N, 77.4'W), College (69.9dN, 147.8°W).
berg, 1978). However lacking an acceptable physical explanation such observa-
tions have been hitherto viewed with scepticism. The highly variable portion
of the sun's spectrum accounts for only about 10 of its total luminosity
which varies by no more than 1.0% over times measured in years (Livingston,
1978;Willis,1976) . Thus the primary driving force for the earth's atmosphere,
solar heating, is essentially constant. The total energy involved in atmo-
spheric electrical disturbances is about 10_J of its kinetic energy, while the
average solar magnetic field in the neighborhood of earth is about 10-^ of its
surface geomagnetic field (Dolezalek and Reiter ,1974) .
Recently a hypothesis to explain the apparent linkage between solar acti-
vity and terrestrial weather has been developed on the basis of a quantitative
consideration of the ionosphere - earth - thunderstorm electric circuit in
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Wilson's model (Markson, 1978 :Fig. 7) . As shown in the figure some 90% of the
circuit resistance is in the ionosphere to thundercloud-top portion, while
thundercloud-bottom to ground accounts for 10%. Through fair-weather regions
ionosphere-to-ground resistance is very small in comparison because of the
relatively large cross-sections involved (analogous to many wires connected in
parallel). The ionosphere-thundercloud resistance thus controls the current
flow in the global atmospheric electrical circuit. According to the hypothe-
E - 11
sis, it is this resistance which responds to solar activity and other events
that alter the upper atmosphere conductivity between electric storm cloud-top
and the ionosphere, affecting storm activity (Markson,1978) . This also ex-
plains the observation that the correlation between solar activity and thun-
derstorm frequency generally increases with latitude, being greatest in auro-
ral regions, where solar events more strongly perturb the atmosphere (Roble
and Hays, 1979). However these considerations alone cannot account for the
magnitude (10-30%) of the changes in ionospheric potential observed in asso-
ciation with solar events. The observations can be explained by the existence
in the mesosphere - between ionosphere and stratosphere - of a vertical elec-
tric potential about 100 kV in magnitude which can be "shorted" by radiation-
induced ionization to add onto the lower atmosphere potential of about 300 kV.
Experimental evidence supports the existence of such a field (Hale and Croskey,
1978).
This model cannot account for all the observed geoelectric fluctuations.
A full understanding requires one to consider other voltage generating mech-
anisms in a circuit extending from ground up to the magnetopause (Hays and
Roble, 1979;Akasofu, 1979 :Fig. 8) . Neither the ionosphere nor the magnetosphere
are actually isotropic homogeneous conductors. Electric potentials perpen-
Fig. 8 Global electrostatic model (Roble and Hays, 1979, p. 52).
12
PRECIPrTATED
ELECTRONS
SCATTERED
ELECTRONS
ELECTRON
STREAM
Fig. 9. VLF wave interactions with the magnetosphere (Park and Helliwell, 1978)
dicular to geomagnetic field lines are generated from motions of plasma inho-
mogeneities across the field lines (Goldberg and Herman, 1979) , and contrary to
what one might suppose from the laws of motion obeyed by charged particles in
magnetic fields, electric potentials exist along geomagnetic field lines as
well (Kellogg and Weed, 1969). The magnetospheric potential distribution can
impress itself onto the ionosphere so that the latter is not an equipotential
surface (Falthamar ,1969) . It has been experimentally verified that iono-
spheric electric fields perpendicular to magnetic field lines can then map to
low altitudes (Kelly and Mozer,1975). Further effects involve VLF spherics
arising from both natural (e.g. lightning flashes) and man-made sources
(powerlines harmonic radiation - see Sect. 5) which propagate along geomagne-
tic field lines and can produce electron precipitation fluxes 10° or more
times the input wave power (Park and Helliwell, 1978:Fig. 9) .
It increasingly appears that the mesosphere and stratosphere act as a
buffer region between the troposphere and the upper atmosphere where small
perturbations of local parameters in response to electromagnetic influences
can be amplified into major effects on energy transport and conversion in the
lower atmosphere. A quantitative description of the connection between geo-
electromagnetic disturbances and terrestrial weatber remains one of the major
unresolved problems in contemporary geophysics.
3. GUIDELINES FOR EXPERIMENTAL WORK
In the evolving theories of sun-weather coupling the stratosphere and
lower mesosphere act to amplify and transmit solar fluctuations down into the
troposphere. The major impediment to the study of this mechanism is that the
energy ration of extra-terrestrial corpuscular radiation (galactic and solar
cosmic rays) to insolation is extremely small on the global scale. However
13
at high latitude, during local winter, this ration locally is significantly
larger that the global mean, and sun-weather correlations are strongest in
the poleward regions (Herman and Goldberg ,1978) .
There are several categories of energetic radiation which impinge on the
upper atmosphere. Galactic cosmic rays, which are modulated by solar activity,
are the dominant influences on atmospheric electrical properties between 5 and
30 km altitude. Solar proton events, though infrequent, can enhance ioniza-
tion by several magnitude orders at the 30 km level. Relativistic electron
precipitation is far more frequent and may possibly modulate stratospheric
heating by inducing changes in ozone concentration. Finally in the auroral
zone, frequent local electron precipitation events often produce significant
bfiem£>i>£Aahli±n.Q X-rays. The conversion of electron energy to X-rays allows
energy to penetrate to depths of atmosphere lower than the absorption height
for the parent electrons (Goldberg , 1978) . In addition, electron precipitation
can be affected by human electromagnetic activities, such as harmonics radia-
tion arising from the transmission of electrical power (Sect. 5).
Thus experimental investigations into the "solar activity - atmospheric
electricity - weather link" must concentrate on monitoring energy deposition
in the atmosphere and concomitant effects on ozone concentration, conductivity
and heating (Fig. 10).
A complete description of global electrical response to solar and geomag-
netic influences would require auroral zone measurements to be supplemented at
lower latitudes as well. Because of the importance of mesospheric fields to
the complete global electrical circuit, rocket as well as balloon measurements
would be needed. The most efficient way to acquire the required data would be
the use of low cost meteorological rockets such as are widely used for wind
and temperature measurements equipped with electric field and charged particle
sensors.
4. GEOELECTROMAGNETIC INFLUENCES ON MAN-MADE SYSTEMS
Electric and magnetic fields are not limited to the atmosphere, but pene-
trate into the solid earth as well. If one were to install two earthed elec-
trodes separated by, say 200 m, and record the potential difference between
them as a function of time, one would observe voltage fluctuations on the
order of several millivolts ranging in period from a few seconds to several
hours (Hessler, 1976) . Some of these "earth currents" are often called "geo-
magnetically induced currents", as they manifest themselves in conjunction
with solar magnetic storms.
In the simplest picture of how solar activity affects the terrestrial
fields, the solar wind carries charged particles to the earth which are de-
flected by its magnetic fields to form encircling sheet currents in the
magnetosphere (Fig. 11). Variations in the magnitudes of these currents in
response to the fluctuating solar wind, and in their positions induce changing
electric and magnetic fields (Levine, 1966;Hermance, 1978) . Additionally,
charged particles with sufficient energy can penetrate into the magnetosphere
and become trapped in orbits about the geomagnetic field lines. Fields from
these particles induce earth currents quite different in character (Figs.
12a, b) from those due to sheet currents (Fleming and Keller, 1972) . These
particles are also affected by electromagnetic radiation from man-made systems.
Such man-made effects will be discussed in the next section. The ionosphere,
E - \k
\\\
v^ \ \ \
ELECTRONS \ \
\ \ E<150keV \ \
\ \ \ \ \ \
Fig. 10 Artist's depiction of the atmospheric X-ray emission telescope
(AXET) concept and objectives (Goldberg ,1978 , p. 24).
being a conducting medium, serves to screen certain frequency components
arising from the aforementioned magnetospheric currents. The ionosphere
itself however is variable, so that the total field variability at the earth's
surface is due both to magnetospheric current fluctuations and to ionospheric
perturbations (Fleming and Keller ,1972) . Typical geomagnetic field fluctua-
tions are about 2X10--5 of normal intensity, but go as high as 4*10 of normal
(Bartels and Fanselau,1938) .
In accordance with Faraday's law, changing magnetic fluxes induce elec-
tric fields, and thus currents in the conducting terrestrial surface. The
frequency energy density spectrum of the induced terrestrial electric fields
is given by tt =Z-kj where E=|e|, H=|h|, and f is the frequency. Z is the
total impedance which depends both on frequency and local geology (Wait, 1962;
Goddard and Boerner, 1979) .
These induced electric fields can introduce currents in such systems as
grounded electrical power and communications systems and pipelines (Lanzerotti,
1977; Acres Report ,1975) . Electric potentials of up to 7 V/km have been ob-
15
PLASMA MANTLE
PLASMA
PAUSE
PLASMA SHEET
MAGNETOPAUSE
SOLAR
WIND
VAN ALLEN
BELTS
MAGNETOSHEATH ^^^^^^0^U^NTS
DAYSIDE CUSP^^v^^^g^^^^^^^^^^^^f
BOW SHOCK
Fig. 11 Model of the earth's nagnetosphere (Levine,1966, p. 47).
served, the effect generally being stronger with increasing latitude reaching
maximum in the auroral belts (Albertson and VanBaelen, 1970) . Quasi direct
currents amounting to hundreds of Amperes have been observed during solar dis-
turbances on long systems such as pipelines and electrical transmission lines
(Lanzerotti,1977;Akasofu and Merritt ,1979;Goddard and Boerner, 1978; Acres Re-
port, 1975 : Figs. 13a, b) .
Principal effects are half -cycle saturation of magnetic devices such as
power and current transformers, and misoperation of protective devices such as
relays and circuit breakers. System shutdown is possible under extreme condi-
tions (Albertson and Kappenmann, 1978) . The Alaska pipeline lies in a region
which experiences geomagnetic disturbance energies up to 100 times greater
than those which occur in most of the middle United States (Campbell, 1978) .
Currents of up to several hundred Amperes have been observed which could con-
siderably shorten its lifetime through enhanced corrosion as well as inter-
fering with safety ard control instrumentation (Procter ,1976;Lanzerotti, 1977;
Akasofu and Chapman, 1972) .
It must be stressed that effects of solar induced currents are not pro-
portional to current magnitude but increase rapidly above a certain threshold,
e.g. when the half -cell potential oxidation potential is exceeded for pipeline
corrosion, or when a shutoff current or voltage is reached for power system
safety devices (Fleming and Keller, 1972) .
16
20,45
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Fig. 12a; Hayashi, Oguti, Watanabe et al, 1978, p. 627
1 A frequency-time
spectrogram of chorus
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harmonics.(a), along with
induction magnetograms
of the magnetic horizontal
component recorded at
Riverton, Star Lake and
Thompson (b). The
ELF-VLF signals (mag-
netic component) were
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antenna whose plane lay
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frequency band below
1 kHz. Their enhance-
ments start coincident
with the initiation of the
rapid negative deflection
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with frequency time spectrograms of chorus emission and power line harmonics
shown below; Hayashi, Oguti, Watanabe et al , 1978.
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5. EFFECTS OF MAN-MADE SYSTEMS ON THE MAGNETOSPHERE:
POWERLINE HARMONIC RADIATION (PLHR) .
On the other hand, man-made systems can discernably affect the geoelec-
tromagnetic environment. As can be seen from Fig. 14 human electromagnetic
influences on the environment are not always the product of advanced tech-
nology. The local custom of lighting bonfires on certain occasions gave rise
to the observed Sunday variations. Chalmers (1952) and Muhleisen (1953) found
the geoelectric field affected as far as 7 km distant from 133 kV electric
power lines. Only rather recently however have the effects of human electro-
magnetic activities come to be observable on a global scale. Bullough,
Tatnal, and Denby (1976) conclude that powerline harmonics originating in the
earth's industrial regions are responsible, at least in part, for the forma-
tion of the 2<L<3 electron slot between the inner and outer radiation belts
in the magnetosphere. Here L is the magnetic shell parameter, which in a
E
\
>
300
260
c
o
a.
200
140
100
\
Diurnal variation of potential gradient in Samoa. (From
Sapsford, 1937, Fig. 1, p. 157.)
rSunday-overage values based
Jl.
on 40 days
JSunday to Saturday (inclusive)
\ I - 264 days
londay to Saturday (inclusive)
Fig. 14; Chalmers, 1967, p. 166
Percentage occurrence of emissions with intensity
>4.8xl0-15 W m"1 Hz"1 at 3.2 kHz, annual electric power
consumption (in GWh mile~H and thunderstorn occurrence for
the USA Kp<2+. , 1967 Summer (May, June, July).
-•-•-•-•, 1967 Autumn (August, September, October).
Relative thunderstorm occurrence: summer/autumn 4 (see
A'
Fig. 15; Bullough et al, 1976, p.
402,
19
modified dipole model of the geomagnetic field gives the distance in earth
radii where a field line crosses the equatorial plane. The intersections of
these magnetic shells so defined with the terrestrial surface also specify a
latitude-like coordinate (Egeland et al,1973). Helliwell, Park and Luette
(1977) have found that VLF chorus activity has the highest probability of
occurrence in regions which are threaded by geomagnetic field lines passing
through industrial zones (Figs. 15 , 16) . These results have been explained as
arising from powerline harmonics that leak into the magnetosphere and, after
amplification up to 1000-fold by natural mechanisms, stimulate the recorded
emission through cyclotron interaction with trapped electrons. In this way
man-made radiation can manifest itself far out of proportion to its initial
strength thousands of kilometers from its origin (Park and Chang , 1978 ; Park
and Miller, 1979) . However, according to Thorne and Tsurutani (1979) power-
line harmonic radiation does not play any major role in the non-adiabatic
dynamics of radiation belt electrons (Fig. 16c). This finding will require
well designed experiments of unbalancing HV-AC powerlines and forcing radia-
tion of prespecified frequencies. We are going to carry out measurements of
these design requirements during the forthcoming summer in Manitoba.
The distinction between man-made effects on nature, and natural effects
on man-made systems is not always clearly defined. There is increasing
evidence that powerline harmonic radiation can initiate or enhance thunder-
storm activity (Bullough and Kaiser , 1978) . If Park and Helliwell' s (1971)
suggestion that thunderstorm electric fields create magnetospheric ducts
proves correct, then powerline harmonics induced thunderstorm activity could
lead to further enhancement of harmonic radiation in a self-sustaining cycle
(Bullough et al,1976). Such an event may well have contributed to the July
1977 Northeastern U.S. blackout (Corwin and Miles, 1978) which was preceded by
geomagnetic and electric storm activity (Fig. 17). Hayashi et al (1978) show
how geomagnetic disturbances during the September 1977 storm have lead to
excessive PLH radiation along one of Manitoba Hydro's extended HV-AC lines,
an event which was concurrent with a substantial increase in electric storm
activity along Lake Winnipeg and also extending into the Nelson River basin
(Fig. 18). These observations are corraborated by statistics provided by
Manitoba Hydro and the Canada Department of Environment indicating that
thunderstorm activity has increased coinciding with the increasing development
of HV-DC/AC powerlines in Manitoba. In particular, there seems to be evidence
that electric storm activity in the interlake region between Lake Manitoba and
Lake Winnipeg has increased since the activation of a 450 KV (1.2 GW) DC
powerline intertieing the Nelson River electric power generating base with
Winnipeg over a distance of about 1000 km (Fig. 18). It would be desirable to
employ a network of spherics counters and integrators over the regions of
interest. However, it should be noted that detection and monitoring methods
of electric storms have been improved and careful re-investigation of these ob-
servations is required. In this context, we were made aware most recently of
the statistics compiled in (Stringf ellow, 1974) which requires subtle re-
examination. In case the statistics relating powerline outages due to light-
ning with the eleven year solar cycle are as definitive as shown in Fig. 16c,
such statistic should show up elsewhere. Definitely, basic statistical ana-
lyses of powerline outages due to geoelectromagnetic disturbances are war-
ranted and we should draw particular attention to the research reported in
(Lethbridge, 1979) where statistical relationships between thunderstorm acti-
vity and solar magnetic boundary crossing events are discussed. Within this
E - 20
[""INC) DATA ]SiO-20% fflB20-40% Bi>40%
80
330 0 30 60
DIPOLE LONGITUDE
50 180
Chorus occurrence frequency in invariant dipole coordinates. Each bin represents
a magnetic flux tube extending from hemisphere to hemisphere with a cross-section of 10°xlOc
invariant latitude and longitude. The histogram shows longitudinal variations in percent
occurrence averaged over invariant latitudes.
Fig. 16a; Hellivell et al, 1977, p. 277.
2S ?ep <6
I209.-4I VT
H<
A spectrogram of chorus activity de-
tected by the Ogo 3 satellite at L = 7.8, 38°
dipole latitude, and 1210 local time. The geo
magnetic activity was moderate (K * 4).
Fig. 16b; Helliwell et al, 1977, p. 276.
E - 21
IX »
■2 IIX »
= (M. »
Z w. •
ISC •
100 •
■3 * •
V/V\
a/VV
sSJ w
I9JO i960
Yeir
"rtfe"
Fig. 16c Annual variation of: a)5-yr. running means of lightning; b)sunspot
number (Stringf ellow, 1974) .
auroral and sub-auroral region, effects of geomagnetic disturbances and PLH
radiation compound along HV lines whose potentials range from about 230 KV to
1.2 MV comparable to or several times greater than the earth-ionosphere poten-
tial (250 KV). This gives rise to reversals in geoelectric field polarity,
increases in local air conductivity influencing charge separation and build-up
within clouds and leading to short range perturbations in the atmospheric
electric environment within the localized region of the Agassiz-Nelson River
basin which could serve as an ideal natural/man-made laboratory for controlled
experiments. Further interdisciplinary studies are required to analyze these
recent findings and to establish the relations with the geo-electromagnetic
and aeronomic environment.
The utility of these proposed studies will be optimized if they are
carried out on inter-regional basis in locations of different geological-
geoelectromagnetic character as well as in a variety of urban/industrial
regions: in the Golden Valley, Alaska; along the US West Coast (BPA) ; the
Central USA (Commonwealth Edison of Illinois); the Agassiz-Nelson River Basin
(Canada); the US East Coast (New York Consolodated Edison); the James Bay
area, Canada (IREQ); and in New Foundland (Boteler ,1979) .
6. GEOELECTROMAGNETIC DISTURBANCE FORECASTING
Many adverse effects of geoelectromagnetic disturbances on man-made sys-
tems could be mitigated or averted given sufficient advance warning.
A major impediment to accurate geoelectromagnetic predictions is that the
connection between solar events and terrestrial effects is seldom direct, but
depends upon intermediate coupling mechanisms through the magnetosphere and
upper atmosphere of which our knowledge is incomplete. For example, auroral
effects on the terrestrial electromagnetic environment arise not only from the
highly variable solar wind but also depend strongly upon the relative orien-
tations of the solar and terrestrial magnetic fields with strong locality
E - 22
17 The New York black out of 14 July 1977 (US Air Force).
E - 23
MwffcMUL
tUjVSotf&V
HV LINES
A/£UTML CU(?flEt/r H£T£*S
(ctesir* d)
Proposed SOQKV HC line
iU Dakota'
B
Twin Cx-titS
Fig. 18 Locations of desired and/or available monitoring stations (Goddard
and Boerner,1978, p. 10).
E - 2k
1200
18-00
Fig. 19 View of the earth from above the N. pole showing N. America being
brought into a "disturbed" zone by the earth's rotation (Boteler,
1979, p. 8).
dependence (Akasof u,1979) . Nonetheless, for lack of more comprehensive data,
most geoelectromagnetic forecasters base their predictions upon observable
solar activity by extrapolating from previously deduced statistical correla-
tions between solar events and subsequent terrestrial effects (Allen, 1977) .
This approach yields reasonably accurate predictions for periods up to a few
days, but is unreliable for longer periods. This is due in part to the fact
that we cannot accurately predict of the birth and subsequent evolution of
solar disturbances, and in part to the sun's rotation which can suddenly bring
into view matured disturbances which formed on its unobservable side (Purple
Mountain Observatory, 1978) . Despite the close connection between the terres-
trial geoelectromagnetic disturbance cycle and the solar cycle there exist
important differences as well (Feynman,1978) and even short term predictions
based on solar observations alone become increasingly error prone with in-
creasing latitude (Hruska,1979) . As shown in Fig. 20 certain types of distur-
bances are not global but manifest themselves through a band of local times.
As the earth rotates different regions will successively pass through the
disturbed zone. Specific quantitative predictions on disturbances of this
sort must be based on more than simple statistical correlations between solar
events and global means of geoelectromagnetic parameters.
Future progress in geoelectromagnetic forecasting will require detailed
monitoring of the electromagnetic environment not only over the terrestrial
E - 25
Fig. 20 A diagram showing ISEE-1 and -2 in orbit about the earth and ISEE-3
at the forward libration point (Ogilvie,1978, p. 151).
surface but extending outward to tens or hundreds of earth radii. This data
would also serve as a basis to advance theoretical understanding of solar and
magnetospheric electromagnetic processes which would allow more extended fore-
casts than are presently possible. In view of mounting evidence for geoelec-
tromagnetic effects on weather and climate, the data might prove useful for
weather forecasting as well.
A first approach in this direction was made with_the launch of the Inter-
national Sun-Earth Explorer (ISEE) satellites to monitor the solar wind and
interplanetary magnetic field. One satellite (ISEE-3) will be orbited about
an earth libration point situated at about 240 earth radii in the sunward
direction (Ogilvie et al,1978:Fig.21) . Akasofu (1978) has developed a formula
to compute both the occurrence and magnitude of magnetospheric substorms ob-
servied in the zuroral zone, given the upstream values of solar wind velocity
and interplanetary magnetic field direction and magnitude. As the solar wind
requires about one hour to traverse the 240 earth radii from the ISEE-3, this
satellite will permit quantitative predictions about one hour in advance.
The next step is to complement satallite monitors with a network of
ground-based recorders across the auroral zone to measure geomagnetic fields,
atmospheric electric fields and earth surface potentials. The ultimate ob-
jective is to monitor all important inputs into the sun-magnetosphere-earth
system simultaneously with major geophysical outputs (geomagnetic field, at-
mospheric electric field, etc.) along with weather-related parameters. This
will be the basis to construct cause-effect models from which can be derived
quantitative advance prediction algorithms.
7. OVERALL RESEARCH ASPECTS
The possibility that man-made electrical systems, their radiation ampli-
fied in interaction with natural phenomena, might produce geo-electromagnetic
perturbations on a global scale emphasizes the need for conclusive investiga-
tions well in advance of planned extensions of large-scale power transmission
systems farther into the geo-electromagnetically active regions. Such inves-
tigations will require simultaneous recording of geomagnetic, geoelectric, and
atmospheric electric parameters as well as currents induced in man-made sys-
tems at several locations spread over the Northern and Southern hemispheres.
E - 26
The effects of powerline harmonics radiation and its interaction with the
magnetosphere/magnetopause will require controlled experiments including un-
balancing and forced radiation of powerline sections in regions accessible to
ground-based, balloon, rocket and satellite borne instrumentation such as can
be provided by Manitoba Hydro, BPA, Commonwealth Edison, etc. Detailed stu-
dies on how induced currents will affect ground-based transmission systems
will have to be carried out simultaneously in collaboration with the utilities
and manufacturers of HV DC converters and AC transformers. Research on many
of these aspects has been initiated recently. Detailed outlines on specific
projects are under preparation and will be presented separately.
8. LOCATIONS
There exist several prime locations to carry out the proposed research
which requires the utilization of large-scale electric powerlines and oil/gas-
pipelines for carrying out controlled experiments. A ncutuAH-gZvcn tabo^iato^iy
Jib the. AgaA-biz-NclAon Rvjqa baAZn tMiMi zxt<LY\iiDn -Into th<t Hud&on Bay am cznt-
HjoJL UonthoJin Am2Ax.ca. This region lies within the sub-auroral to auroral
belts and large-scale HV-AC/DC powerlines of several Gigawatt power extending
from about 58°N, to 45°N latitude are being developed by Manitoba Hydro and
MAPP (Fig. 18). Several geophysical laboratories can easily be set up by
expanding recording stations of geomagnetic, geoelectric, and meteorological
parameters.
Furthermore, the facilities of the Bonneville Power Administration as
well as of Commonwealth Edison of Illinois are also located ideally and should
provide two essential additional sites to carry out controlled PLHR experi-
ments. Collaboration with Manitoba Hydro, MAPP, BPA and Commonwealth Edison
have been established to initiate this research on a larger scale.
9. BENEFITS
The proposed international, interinstitutional and interdisciplinary
research should be of immediate interest to the sciences of aeronomy, geo-
physics and geology as it should provide a host of hitherto unavailable
factual data. It should also be of paramount importance to advancing the
technology of electrical energy, oil and gas transmission in geo-electromag-
netically active regions with the objective of reducing uncontrollable elec-
tromagnetic radiation and systems outages caused by transformer and relay
malfunction or unwarranted corrosion. A byproduct of these studies will be an
exhaustive spectral analysis of VLF background noise induced along supra-long
conductor systems which should be of immediate interest for military communi-
cations. These studies will stimulate fruitful interchanges among various
military, industrial and academic institutions.
10. ACKNOWLEDGEMENTS AND SUPPORT
The initiation of this research was and is supported in parts by Manitoba
Hydro, NSP, EPRI , NSERC-Canada (Grant No. G 0087), the Space Research Facility
Branch of NRC-Canada (particularly its newly established ballooning and
E - 27
rocketing site at Gimli, Man.), and by a UICC Grant (No. RB 301-22-33-306).
This interdisciplinary study will be carried out in collaboration with
Professor Donald E. Olson, U. of Minn/Duluth; Professor Vernon D. Albertson,
U. of Minn/Minneapolis; Professor Robert A. Helliwell, SU, Stanford; Professor
Tomiya Watanabe, UBC, Vancouver, B.C.; Professor Takeo Yoshino, Univ. of
Electrocomm. , Tokyo. We are currently seeking active participation of other
researchers involved in similar studies and we are seeking additional finan-
cial support.
REFERENCES
Acres Consulting Services Ltd., "Study of the disruption of electric power
systems by magnetic storms", Report for Dept. of Energy Mines and Re-
Sources, Ottawa, Canada, March 1975.
Akasofu, S-I. , "Interplanetary energy flux associated with magnetospheric
substorms", International STP Proceedings & Workshop, Boulder, Colorado,
April 1979.
Akasofu, S-I. and Chapman, S. , Solar Terrestrial Physics, Clarendon Press,
Oxford, 1972.
Akasofu, S-I. and Merritt, R.P., "Electric currents in power transmission
lines induced by auroral activity", To be published in Nature, 1979.
Albertson, V.D. and Kappenmann, J.G., "Magnetic storm effects in electric power
systems and prediction needs", International Solar-Terrestrial Predic-
tions Proceedings and Workshop Program, Preprint no. 77, November 30,1978.
Albertson, V.D., Kappenman, J.G., Mohan, N. , Skarbakka, G.A. , "Load-flow in
the presence of geo-magnetically- induced currents", IEEE PES Meeting,
Vancouver, B.C., July 15-20, 1979, Paper No. F79 702-2.
Albertson, V.D. and Van Baelen, J. A. , "Electric and magnetic fields at the
earth's surface due to auroral currents", IEEE Trans, on Power Apparatus
and Systems, Vol. PAS-89, No. 4, April 1970.
Allen, J. H. , "Relative magnitudes of major magnetic storms by the Ap measure,
and their frequency distribution from 1932-76", presented at the IAGA/
IAMP Symposium, Seattle, Wash., August 1977, 9 pages.
Anderson, C.W., Lanzerotti,L. J. , et al, "Outage of the L4 system and the geo-
magnetic disturbances of 4 August 1972", Bell Syst .Tech. J. 53 (9) , pp. 1817-
1837.
Bartels,J. and Fanselau,G., "Der erdmagnetische Sturm vom 16 .April, 1938" ,
Naturwissenschaf ten 26(19), pp. 296-298, 1938.
Boteler,D.H. , "The problem of solar induced currents", International Solar-
Terrestrial Predictions Proceedings and Workshop Program, No. 150, 1979.
Bullough,K., et al, "Man-made elf/vlf emissions and the radiation belts",
Nature 260(5550), pp. 401-403, 1976.
E - 28
Bullough,K. , Kaiser, T.R. , "Ariel 3 and 4 studies of power line harmonic ra-
diation", URSI, 1978 General Assembly, Helsinki, Finland.
Campbell, Wallace H. , "Introduction of auroral zone electric currents within
the Alaska pipeline", Pure and Applied Geophysics 116, pp. 1143-1173, 1978 .
Chalmers, J. A. , Atmospheric Electricity, Pergamon Press, London, 1967.
Chalmers, J. A. , "Negative electric fields in mist and fog", J. Atmos . and
Terr. Phys. 2, pp. 155-159, 1952.
Corwin,J.L. and Miles, W.T., "Impact assessment of the 1977 New York city
blackout", Prepared for US Dept. of Energy by Systems Control, Inc . , 1978.
Dolezalek,M. and Reiter,R., ed. Electrical Processes in Atmospheres, Proceed-
ings of the 5th International Conference on Atmospheric Electricity held
at Garmisch-Partenkirchen (Germany), 2-7 September 1974, Steinkopff
Verlag GmbH & Co., K.G., Darmstadt.
Egeland,A. , Holter, 0. , Omholt,A. , Cosmical Geophysics, Scandinavian Univer-
sity Books, Universitetsf orlaget, Oslo, 1973.
FHlthamar ,G-G. , "Electric fields in space - a survey", in Planetary Electro-
dynamics , S.C. Coroniti, J. Hughes, ed. Gordon and Breach, New York, 1969.
Feynman,J., "The 21st solar cycle aa index of geomagnetic activity", Inter-
national Solar-Terrestrial Predictions Proceedings and Workshop Program,
Preprint No. 57, November 1978.
Fischer, H-J. and Muhleisen,R. , "Variationen des Ionospharenpotentials und der
Weltgewittertatigkeit im 11-jahrigen solar en Zyklus", Meteorologische
Rundschau 25(1), pp. 6-10, 1972.
Fleming, D. B. , Keller, G.V., "Research on the probability of occurrence of
unusually large earth current storms", Final Report for the Bonneville
Power Administration, Portland, Oregon and U.S. Bureau of Reclamation,
Denver, Col., Submitted by Colorado SchooL of Mines, Golden, Colorado,
March 1972.
Fleming , J. A. , ed. Terrestrial Magnetism and Electricity, Dover, New York, 1949.
Goddard,W.R. , Boerner,W-M. , et al, "Effects of solar induced currents on
electric power transmission systems of Manitoba Hydro in central Canada",
Proc. of 21st Plenary Meeting ICSU-COSPAR 21, Innsbruck, Austria, 29 May-
10 June, 1978, Paper no. 40-1.
Goddard, W.G., Boerner, W-M. , "Prediction of Solar Induced Currents and Effects
on Power Transmission Systems in Central Canada", International Solar-
Terrestrial Predictions Workshop, April, 1979, Boulder, Co., 15 pages.
Goldberg, R. A. , "An experimental search for causal mechamisms in sun/weather-
climatic relationships. Symposium/Workshop on Solar-Terrestrial In-
fluences on Weather and Climate, Ohio State University, Columbus, Ohio,
July 24-28, 1978.
E - 29
Goldberg, R. A. and Herman, J. R. , "Coupling processes related to the sun-weather
problem", Invited review for the International Solar-Terrestrial Pre-
dictions Workshop, Boulder, Colorado, April 23-27, 1979.
Hale,L.C. and Croskey ,C.L. , "Auroral effects on atmospheric electric fields",
Oct., 1978. Submitted to Nature.
Hayashi,H. , Oguti,T., Watanabe,T., Tsuruda,K., Kokubun,S., Horita,R.E., "Power
harmonic radiation enhancement during the sudden commencement of a mag-
netic storm", Nature _275 (5681) , pp. 627-629, October 1978.
Hays, P. B. and Roble,R.C, "A quasi-static model of global atmospheric electri-
city I. The lower atmosphere" , J. Geophys. Res. (Space physics) , 1979, in press.
Helliwell,R. A. , Park,C.G., Luette,J.P., "Longitudinal variations of very-low-
frequency chorus activity in the magnetosphere: evidence of excitation
by electrical power transmission lines", Geophy. Res. Lett. 4_, No. 7,
pp. 275-278, July 1977.
Herman, J. R. and Goldberg, R. A. , "Sun, weather and climate", NASA SP-46, Scien-
tific and Technical Information Branch, NASA, Washington, D.C., 1978.
Hermance, J.F. , "Electromagnetic induction in the earth by moving ionospheric
current systems", Geophys. J.R. Astr. Soc. 55_, pp. 557-576, 1978.
Hessler, V.P. , "Causes, recording techniques and characteristics of telluric
currents", Materials Performance, pp. 38-47, April 1976.
Hruska, J. , "Forecasts of geomagnetic activity by Ottawa Magnetic Observatory:
their reliability and application", International Solar-Terrestrial
Predictions Proceedings and Workshop Program, No. 110, December 1978.
Israel, H. , Einfuhrung in die Geophysik, Springer-Verlag , New York, 1969.
Kellogg, P. J. and Weed,M., "Balloon measurements of ionospheric electric
fields", in Planetary Electrodynamics, S.C. Coroniti, J. Hughes, ed.
Gordon and Breach, New York, 1969.
Kelly, CM. and Mozer,F.S., "Simultaneous measurement of the horizontal com-
ponents of the earth's electric field in the atmosphere and in the
ionosphere", J. of Geophysical Res. 80(22), pp. 3275-3282.
Lanzerotti,L. J. , ed. Impact of ionopsheric/magnetospheric processes on terres-
trial sciences and technology, SCOSTEP Survey, April 1977, Presented at
the Solar Terrestrial Physics Conference, Innsbruck, Austria, June 1978.
Lethbridge,M.D. , "Thunderstorm frequency and solar sector boundaries", Proc.
of Ohio University Symposium on Solar Weather, July 1978.
Levine,M.A. , "Plasmas in Space", IEEE Spectrum', pp. 43-47, November 1966.
Livingstone, W. , "Solar input to the terrestrial system", Symposium on Solar-
Terrestrial Influences on Weather and Climate, Columbus, Ohio, 1978.
Markson,R. , "Solar modulation of atmospheric electrification and possible
E - 30
implications for the sun-weather relationship", Nature 273(11) , pp. 103-
109, May 1978.
Mohan, N, Kappenman. J.G., Albertson, V.D., "Harmonics and switching trans-
ients in the presence of geo-magnetically-induced currents , IEEE PES
Summer Meeting, Vancouver, B.C., July 15-20, 1979, Paper No. F79 694-1.
Muhleisen,R. , "Die luf telektrischen Elemente im Groftstadtbereich" , Z. Geophys,
29, pp. 142-160, 1953.
Muhleisen,R. , "New determination of the air-earth current over the ocean and
measurements of ionosphere potentials", Pure and App . Geophy. 84_, pp.
112-115, 1971.
Muhleisen,R. , "Zusammenhange zwischen luf telektrischen Parametern und Sonne-
naktivitat bzw. Nordlichtern" , Kleinheubacher Berichte, Vol. 13, pp. 129-
133, 1969.
Ogilvie,K.W. et al, "Descriptions of experimental investigations and instru-
ments for the ISEE spacecraft", IEEE Trans, on Geoscience Electronics,
Vol. GE-16, No. 3, July 1978. (SPECIAL ISSUE on missions of ISEE SPACE
CRAFTS)
Olson, D.E., "The evidence for auroral effects on atmospheric electricity",
Pure and Applied Geophysics 84, 19711, pp. 118-138, 1971.
Olson, D.E., "The measurement of atmospheric electrical parameters under AC
and DC powerlines", September 1978, to be published.
Park,C.G. and Chang, D. C. D. , "Transmitter simulation of powerline radiation
effects in the magnetosphere" , Geophys. Res. Lett. _5(10) , pp. 861-864,
October 1978.
Park,C.G. and Helliwell,R. A. , "The formation by electric fields of field
aligned irregularities in the magnetosphere", Radio Sci 6_, pp. 299-304,
1971.
Park,C.G. and Miller, T.R., "Sunday decreases in magnetospheric VLF wave
activity", To appear in J. of Geophys. Res., 1979.
Procter, T. G. , "Pipeline telluric current as one phase of a wider inter-
disciplinary technological problem", Materials Performance, pp. 24-28,
August 1975.
Purple Mountain Observatory, "Solar activity forecasting at the Purple Moun-
tain Observatory", International Solar-Terrestrial Predictions Proceed-
ings and Workshop Program, Preprint No. 4, September 1978.
Reiter,R., "Chromospharische Eruptionen der Sonne beeinflussen atmosphMrisch-
elektrische Elemente in der unteren Troposphare", Meteorologische Rund-
schau 25_(1), pp. 1-6, 1972.
Reiter,R., "The electric potential of the ionosphere as controlled by solar
magnetic sector structure", Naturwissenschaf ten 63_, pp. 192-193, 1976.
E - 31
Reiter,R. , "Study to verify patterns of atmospheric potential gradient and
air-earth current after solar flares based upon the geographic distribu-
tion of storm centers", Riv. Ital. di Geofis. 23^3/4), pp. 193-197, 1974.
Reiter,R. and Littfass,M., "Stratospheric-tropospheric exchange influenced by
solar activity", Results of a 5 Yeas Study. Arch. Met. Geoph. Biokl.,
Ser. A26, pp. 127-154, 1977.
Roble,R.G. and Hays, P. B. , "Solar-terrestrial coupling through atmospheric
electric", To be published in NAS-Sun, Weather and Climate, 1979.
Rostoker,G., "Current flow in the magnetosphere during magnetospheric sub-
storms", J. of Geophys. Res. 79(13), pp. 1994-1998, May 1974.
Stacey,F.D., Physics of the Earth, John Wiley and Sons, New York, 1969.
Stringf ellow,M.F. , "Lightning incidence in Britain and the solar cycle",
Nature 249, May 24, 1974, pp. 332-333.
Tatnal,A.R.L. , Matthews, J. P. , Bullough,K., Kaiser, T.R., "Powerline harmonic
radiation and the electron slot", Space Physics Group. Sci. Rep. 1978-1,
Univ. of Sheffield, S. Yorkshire, England, March 1978.
Thorne,R.M. and Tsurutani,B. T. , "Powerline harmonic radiation: Can it sig-
nificantly affect the earth's radiation belt?", Science 204, 25 May 1979,
pp. 839-841.
Volland,H. , Schaefer,J., "Planetary waves and sun weather effects", Proc. and
Workshop on Solar Terrestrial Predictions, April 23-27,1979, Boulder, Col.
Wait, James R. , "Theory of magneto-telluric fields", J. of Res. of the NBS -
D. Radio Propagaton, Vol. 660, No. 5, Sept. -Oct. 1962, pp. 509-541.
Willis, D.M., "The energetics of sun-weather relationship: Magnetospheric
processes", J. of Atmos. Terr. Phys. 38_ 685, 1976.
Wilson, C. T. R. , "On thunderstorm electricity", Phi. Mag. 17, pp. 634-641, 1909.
E - 32
F. SUN-WEATHER PREDICTIONS
THE SOLAR PREDICTION OF CLIMATIC CHANGES
Hurd C. Wi 1 lett
Solar Climatic Research Institute, Inc.
P. 0. Box 20
Cambridge, Massachusetts 021^2
The purpose of this paper is essentially threefold, namely:
1. To set forth in comprehensive form basic observed features of
the hemispheric synoptic patterns of climatic change. It is to the
explanation of these hemispheric patterns, so often lost sight of,
that any specific hypothesis of physical solar control must be
addressed.
2. To note significant statistical relationships between synoptic
pattern sequences of climatic change and the cycles and specific
manifestations of variable solar activity.
3. To offer some tentative suggestions as to possible physical
linkage between disturbing solar impulse and atmospheric response.
In conclusion are offered the author's suggestions as to the best
research approach by which to establish that physical linkage.
Only then can effective prediction models of climatic change be
developed.
INTRODUCTORY REMARKS
The following discussion is based on more than 30 years of first hand
experience by the author in the research of solar climatic relationships and
their application to seasonal and longer-range weather prediction. Fortun-
ately this long period of solar-climatic research was preceded by a 10-year
study of the statistical-synoptic and physical-dynamic behavior of the
general circulation of the northern hemisphere with Rossby and his colleagues
at MIT. One practical result of this joint effort was the initial develop-
ment of the 5-day forecasting technique which subsequently was established in
the U.S. Weather Bureau as the Extended Forecast Section under Namias'
direction.
As early as 1945 it became clear to the author as a result of this
extensive physical-synoptic analysis of the development and prediction of
current hemispheric weather trends, that major changes of the behavior pattern
of the general circulation can not be explained primarily by the internal
F -1
dynamics of the earth-atmosphere system. Similar initial states of the
system do not at all necessarily lead to similar subsequent states, and from
time to time the usual or normal trends of development of the system
suddenly are jolted into quite different and unusual trends.
It was this conclusion that decided the author around 1945 to look
for extra-terrestrial sources of disturbance and control of large scale
changes of the hemispheric pattern of the general circulation. Variable
solar activity is the logical source of such disturbing impulses, and no
evidence turned up to date indicates that we need look further.
Abnormality or change of climate is merely the mean weather expression
of persistent anomaly or change of the pattern of the general circulation (GC)
A climatic anomaly or trend is always associated causally with a correspond-
ingly persistent anomaly or trend, usually of hemispheric or worldwide extent,
of the mean state of the GC. Such anomalous mean states of the GC are
seldom persistently present as a steady state over a long period of time, but
rather persistently recurrent in a stronger state or more frequently than
normal.
Basically the anomalous states or trends of the GC that set the climatic
patterns fall into two distinct categories, the zonal and the meridional.
Since these two forms or patterns of climatic change tend to be as
distinctive in regime and probable cause as they are in form, to keep the
discussion of a very complex problem as simple and clear as possible, each of
the two basic categories of change is discussed in turn as to observed
synoptic pattern, as to statistical relationship to cycles of solar activity,
and as to possible solar cause. The zonal pattern is considered first as
the simpler and probably more basic.
2. ZONAL PATTERNS OF CHANGE OF THE GC AND CLIMATE
2.1 Long Term Secular Changes
2.1.1 Synoptic
The general circulation of either hemisphere is said to be zonal in
pattern when the two major zonal wind systems, the westerlies of middle
latitudes and the compensating easterlies of lower latitudes are well
developed and dominate the pattern.
The most important climatic contrast, that which is the basis of all
long-term major climatic fluctuations or trends, depends on the progressive
poleward or equatorward shift of the hemispheric zonal wind system from its
normal latitude. The corresponding circulation patterns are referred to as
the high latitude zonal (HLZ) and the low latitude zonal (LLZ) respectively.
The severity of the climatic anomaly depends upon the degree and the
persistence of the latitudinal shift.
F - 2
A number of pertinent synoptic and dynamic features of this basic pattern
of climatic change require brief mention, namely:
1. In terms of the hemispheric GC pattern, this fluctuation is best
described as a contraction (HLZ) or expansion (LLZ) of the circumpolar
cyclonic vortex (CPCV) .
2. The expansion of the CPCV (LLZ) represents an expansion of the polar
climatic zone, such that the maximum poleward gradient of temperature
(latitudinal solenoid field) is shifted from higher to lower middle latitudes.
Coldest winter temperatures in the arctic zone accompany a contracted rather
than expanded CPCV.
3. Correspondingly the jet stream (-JS) or peak westerlies of the upper
troposphere also shift with the solenoid field, and the strength of each
correlates very highly negatively with the latitude (Willett, 1960), i.e.,
there is no tendency to conservation of angular momentum in the expansion
or contraction of the CPCV.
A. The expanded CPCV forces the subtropical high pressure belt
equatorward of its normal latitude into an intense narrow high pressure belt
of strong subsidence bounded on the equatorward side by strong tropical
easterlies (TE) at lower than normal latitude, i.e., high positive correlation
exists between the strength and latitude of the ZW with those of the TE
(Willett, 1960).
5. Corresponding to the strong low latitude jet of the expanded CPCV
the LLZ circulation pattern is marked by an active belt of migratory lows
at lower than normal latitudes, hence the climatic pattern is predominantly
cool and wet in lower middle latitudes, cool and dry in higher middle
latitudes, and warm and exceptionally dry in the narrow subtropical high
pressure belt which imposes hot and dry conditions on regions normally
watered by rains in the northern portion of the equatorial convergence belt.
That belt in turn is exceptionally active producing heavy rains on the
equatorial edge of the low latitude belt of abnormal heat and drought. This
is par excellence the climatic pattern of a glacial as opposed to inter-
glacial epoch.
6. The contraction of the CPCV (HLZ circulation) produces a pattern of
climatic anomaly exactly the opposite of the glacial pattern of the expanded
vortex, i.e., warm and wet in higher middle latitudes, a broad flat
subtropical high pressure belt causing general warmth and deficiency of
rainfall in lower middle latitudes, with a broad inactive intertropical
convergence zone which spreads rain northward into the southern fringe
regions of the normally dry belt of the subtropical high, but with less
than normal rainfall in the tropical convergence zone. This is par
excellence the climatic pattern of an interglacial as opposed to glacial
epoch.
2.1.2 Relation to Long-Term Solar Secular Cycles
A. Observed Relationships
Figure 1 is introduced as the simplest means by which to convey briefly
some picture of the observed secular solar climatic relationships which must
be explained for best predictive application. Only the 80 or 100-year
secular cycle is considered, because there are no statistically reliable
samples of the longer cycles.
In Figure 1 the heavy sunspot number curve is after Eddy (1975) , while
the terminations of the secular cycles and the alternate positive or
negative designation of the predominant polarity of the solar magnetic
field during successive 11-year sunspot cycles are after Sleeper (1972). The
periods of peak warmth (W- to W+) and of peak coldness (C- to C+) are
designated after the following sources:
1. Since 1900, after Willett and Prohaska (1977), Willett (1978)
2. 1850-1900, Smithsonian World Weather Records, Willett (1950)
3. Previous to 1850, the masterful climatic treatise of Bruckner (1890)
The broken curve of predicted sunspot extrapolation and the warm and
cold peaks of temperature departure following 1977 are noted briefly below.
The following features of Figure 1 merit attention and explanatory
comment :
1. The prevalence of extreme coldness (and wetness) in middle latitudes
(strong LLZ circulation) during prolonged periods of very low sunspot
activity, notably the Maunder Minimum (1640-1710), and apparently likewise
during the similar Sporer Minimum about 180 years earlier. These two periods
constitute the backbone of the Little Ice Age, a period of active regenera-
tion and growth of glaciers in middle latitudes. Ten thousand years of a
climate no more severe than that of the Maunder Minimum would bring the
northern hemisphere under an ice sheet like that of the Wurm (Wisconsin)
glacial epoch.
LLZ climates less extreme than that of the Maunder Minimum, corresponding
to less extremely low levels of sunspot activity, occurred during the first
25 years of the 80-year secular cycle starting in 1795, and the first 40
years of the 100-year cycle starting in 1875. A similar trend to cooler and
wetter conditions in middle latitudes started in the late 1950' s, exactly
analogous to that in the 1770' s, each time at the very active sunspot peak
late in the 100-year cycle. This is the cooling trend frequently attributed
to increased particulate matter in the atmosphere (Bryson, 1974). This
trend was accurately predicted by Willett (1951) by solar analogy well in
advance, to moderate slightly in the early 70' s, and to continue to even lower
extremes in the 80' s and 90' s like the analog period. Also accurately
forecast by Willett (1955), as part of the predicted LLZ circulation pattern,
was an abrupt decrease of severe hurricanes on the middle and north Atlantic
coast of the U. S. in the 60's, to continue for the rest of the century
(see 3 below) .
140
1610 1620 1630 1640 1650 1660 1670 f'680 1690 1700 1710 1720 1730 1740
MAUNDER C+MIN
1740 1750 1760 1770* 1780 179"! 1800 1810 f 1820 j 1830 1840
w+ c~ c+ w c+
1850 i860 I 1870
w~
200
1870 iseof 1890 1900 1910 1920 1930 I
C
940 igbOf" I960 l9 70fl3B0A '9<
+ c-
w
1380 |
;~ I
9Cff 20C0 f 2010
c+ w
c w
FIG- I . SUNSPOT NUMBER AND CLIMATIC RECORD
F - 5
2. Rising temperatures in middle latitudes (HLZ pattern) occurring
during the period of most active increase of sunspots in the middle or later
part of the secular cycles. Notably peak temperatures, the warmest since
the Little Ice Age, occurred about 20 years before the end of each of the
100-year cycles, in each case some 4 or 5 years before the highest sunspot
maximum since long before the Little Ice Age, warmer in the recent cycle of
higher sunspot activity. In the 80-year cycle there were two equal sunspot
peaks somewhat lower in number, one in the middle and one at the end of
the cycle, preceded in each case by peak warmth correspondingly less extreme.
The rising trend of temperature accompanying the rapid rise of sunspot
activity following 1920 is that frequently attributed to C02 (Bryson 1974) .
3. Dichotomy of the current sunspot trend (Figure 1 and Table 1).
The prediction by Willett (1978) in early 1977 of further intensification
of the LLZ pattern beyond 1980 (peak of wetness and coldness in lower middle
latitudes to occur in the 90 's - Figure 1) was based on the assumption that
sunspot activity as suggested by the heavy dashed line would continue
analogously to that at the end of the 100-year cycle 180 years before. The
upper line of C and W designations at the end of Figure 1 are taken from the
analogous period.
Even by early 1977 it was apparent that sunspot activity was on a trend
unprecedented in the early part of a secular cycle. After a record high
minimum in 1976 (average RSS 12.5) the number has turned sharply upward
towards a predicted strong positive maximum by the end of 1979 (light
dotted curve in Figure 1). This trend is at complete variance with the
marked sunspot inactivity, long 11-year cycles with low maxima and very low
minima which initiated not only the analog 80-year cycle in 1795, but also
the two 100-year cycles in 1695 and 1875. Is this sudden burst of sunspot
activity merely a temporary aberration, or does it presage a return to the
high activity and short 11-year cycles pertaining to the later active half
of the two last 100-year cycles? The second alternative is suggested by
the light dotted curve which portrays 1975 as a mirror point from which to
retrace recent high sunspot activity with the normal reversal of the solar
magnetic polarity of the successive 11-year cycles.
The solar climatic sequence suggested by the light dotted sunspot curve
would radically alter the climatic predictions based on the early 19th
century analog. It would call for a brief cold wet (LLZ) period in middle
latitudes in the mid 80' s, followed by a return to markedly warm dry (HLZ)
conditions by the early 90' s (at the time indicated to be of most severe
coldness by the analog prediction) , and a period of severe climatic stress
(Section 2) by the late 90 's. In this connection it should be noted that the
last several years have been quite stressful climatically as required by a
strong positive sunspot max in 1979-80. At any rate it is to be expected
that the current tangent on which sunspot activity appears to be taking off,
if long continued, will play havoc with the analog solar climatic predictions.
B. Tentative Suggestions as to Solar Explanation of Observed
Relationships
There are three features of the observed long-term secular solar climatic
relationships presented in Figure 1 of significance for this explanation by
variable solar activity, namely:
1. In the long secular cycles by far the most statistically significant
changes of temperature (and probably also of rainfall) occur in lower
latitudes (25°-35°) , during the summer season and in interior continental
locations (predominantly continental as opposed to maritime climate) ,
Willett, 1965a.
2. The periods of greatest coolness and wetness (LLZ climate) tend to
coincide uniformly with the periods of lowest sunspot activity, but broad
zonal warmth and dryness (HLZ climate) tends definitely to precede the
periods of highest sunspot activity in the secular cycle, to coincide more
with the period of most rapid rise of such activity from the quiet to
the active part of the cycle.
3. The LLZ climatic patterns during the quiet portion of the secular
cycle are more uniform and steady in middle latitudes with less short term
fluctuation and geographical contrast than occurs in the HLZ patterns going
into the active half of the cycle.
In the light of the above observational facts we may venture a few
speculations as to how the sun may do it, as follows:
1. Prolonged periods of quiet sun must be periods of little solar
wind or of high frequency u.v. , whereas the black body radiation, including
the low frequency u.v., retain full intensity or may even be enhanced by the
clearness of the solar atmosphere (low activity of chromospheric eruptions) .
2. The effective solar emanations must act, either directly or
indirectly, to produce relative heating of the troposphere in subtropical
latitudes and cooling in lower middle latitudes during long periods of very
low sunspot activity, and the reverse during periods of strongly increasing
sunspot activity.
3. The action of the effective solar emanations during the phase of the
secular cycle of rapidly increasing sunspot number to increase the latitudinal
gradient of temperature between lower middle latitudes and the subtropics
terminates and apparently reverses welJ before solar activity reaches its
peak.
In the light of these facts it might be suggested that the quiet sun
permits a cooler atmosphere in the higher latitudes, probably by the strong
reduction of outbursts of high frequency u.v. and of corpuscular radiation,
hence the reduction of atmospheric ozone (particularly in winter) and of
high level condensation nuclei (ci cloudiness). In addition, the elimination
of strong corpuscular invasions (strong mid-latitude auroral activity) permits
the CPCV to continue undisturbed without breakdown into a meridional
cellular pattern (see Section 2) . On the other hand it is very interesting
to note, using Feynman and Crooker's (1978) geomagnetic activity index for
the strength of the solar wind, that the curve of hemispheric warming of
the first half of the 20th century as given by Willett and Prohaska (1977)
paralleled almost exactly their curve of the increase of the solar wind,
rising slowly during the earlier decades, then more steeply to a pronounced
peak in the early 50' s, and then falling sharply during the following decade.
This suggests an important indirect effect of the solar wind on the Green-
house effectiveness of the earth's atmosphere from mid-latitudes poleward,
perhaps through ozone or high tropospheric cloudiness (through condensation
nuclei) .
2.2 Short Term Changes of the Zonal Patterns
The short term climatic changes range in time period from those
associated with successive phases of the DSS cycle through the quasibiennial
.year-to-year fluctuations of the seasonal climatic anomaly patterns within
one phase of the DSS cycle, down to the monthly and sometimes even weekly
sudden burst changes of the general circulation and attendant climatic
pattern. The basic zonal patterns of circulation and climate HLZ and LLZ , may
fluctuate in any period from the longest secular to the weekly sudden burst,
but the meridional patterns treated in Section 2 have no significant
association with the long secular cycles, but they do with all of the shorter
periodicities from the DSS cycle to the sudden burst changes (sudden
stratospheric warmings) .
The basic zonal patterns of cirulatioh and climate, HLZ and LLZ, are
similar in shape whether they are long term secular or the weekly very
short term, but the latter, being single events, can be much sharper and
more abrupt than the long term, which are statistical averages of a number of
short term events. Hence the short term may be more illuminative of
physical cause than the long term, so that synoptic and physical aspects
of the short term fluctuations are combined in the following discussion.
Figure 2 presents the mean of the DSS cycle as it averaged from 1870-
1970, approximately the years of the last 100-year secular cycle. The
sunspot number graph is a smoothed curve drawn through the eight average
phase numbers. The individual calendar years (1871-1981) entering into each
phase of the DSS cycle, with an indication of the current dichotomy, are
listed in Table 1.
In Figure 2 the average cycle year period of each of the eight phases
is indicated across the middle of the graph. Across the top of the figure
is indicated the tendency to GC pattern predominance during the cycle, and
also the period of peak warmth W or coldness C, as well as of dryness (p-)
or wetness (p+) of 'the mid-latitude climate.
The following synoptic features of the DSS cycle and even shorter term
fluctuations of the zonal circulation (CPCV) from year to year, month to
month and even week to week (see Section 2) are possibly significant for
the explanation of the physical causation of fluctuations of the hemispheric
zonal circulation (CPCV) .
F - 8
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Table 1. Classification of Years 1871-1981
by Phases of Double Sunspot-Cycle,
-+ ... +
Min
R
Max
Min
1890
1871
1872
1877
1879
1882
1885
1888
1891
1872
1873
1878
1880
1883
1886
1889
1892
1892
1874
1879
1881
1884
1887
1890
1915
1893
1895
1900
1903
1905
1908
1911
1916
1894
1896
1901
1904
1906
1909
1912
1917
1917
1897
1902
1905
1907
1910
1913
1935
1918
1919
1922
1924
1927
1930
1932
1936
1919
1920
1923
1925
1928
1931
1933
1937
1937
1921
1924
1926
1929
1932
1934
1955
1938
1940
1942
1945
1947
1950
1952
1956
1939
1941
1943
1946
1948
1951
1953
1957
1957
1942
1944
1947
1949
1952
1954
1977
1958
1960
1963
1966
1968
1971
1975
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from
1978
1959
1961
1964
1967
1969
1972
1976
J 1979 j
' secular
1979
1979
1980
1981
1962
1965
1968
1970
1973
1977
\ 1980 J
analog
1. Note in Figure 2 that whereas the peak of the LLZ cold and wet
circulation pattern (expanded CPCV) is centered on the Min phase of the DSS
cycle, in line with the long term high preference of LLZ patterns for the
periods of very low solar activity, the peak of the HLZ warmth and dryness
is centered on the Min- phase of the cycle, even lower in number than the
Min+ phase, at complete variance with the long term secular cycle record.
The warmth and dryness of the Min- ending in the late R phase is statis-
tically the most significant climatic anomaly of the DSS solar-climatic cycle. All
of the major droughts since 1890 between the Rockies and the Mississippi
Valley followed this pattern. The LLZ coolness and wetness of the Min+
and R" phases are the second most significant statistical fact of the cycle.
In this connection it may be noted that the reversal of the solar
magnetic field is a known fact of the DSS cycle only during the last 100-year
secular cycle, but there is no observational confirmation even of the
existence of a DSS cycle during the previous 80-year secular cycle or
earlier. However, the reversal of the solar magnetic field and of the sunspot
pair magnetic fields certainly affect strongly the magnetic beaming of
solar corpuscular radiation, i.e., the charged particle solar wind, towards
the earth. That this is indeed a fact is confirmed by the observation that
geomagnetic disturbance (C^) which reaches significantly its highest peak
level in the DSS cycle at Max"*" falls very sharply to much its lowest level
of the cycle at Min". From there it recovers only to half of its Max
peak level by Max", but continues upward to a peak at F- significantly below
that of Max , and then to a bottom at Min- much higher than that at Min+
(Willett 1960b) . More and more bits of evidence are pointing to the solar
wind as a primary disturbing influence in fluctuations of the temperature
and GC of our troposphere and lower stratosphere.
10
2. There is a normal seasonal sequence of the hemispheric zonal
circulation (CPCV) , although on occasion this normal sequence may be rudely
interrupted by a complete breakdown or even reversal of the CPCV (Willett
1968). Normally a strong HLZ circulation, strongest in the lower troposphere,
develops rapidly during the middle and late autumn, and trends towards a
peak of LLZ (and JS) by mid or late January. Usually a sudden breakdown of
the strong LLZ circulation and JS occurs in late winter. The CPCV rarely
redevelops normal winter strength again during the spring and summer.
It may be remarked that the steady strengthening and equatorward
expansion of the CPCV which is typical of autumn going into midwinter
parallels the normal seasonal progression of the net loss of heat to space
by the radiational heat balance, i.e., periods of strong LLZ circulation
and CPCV are periods of conditions favorable to the relative cooling of
the atmosphere in higher latitudes. Furthermore the tendency to sudden
breakdown of the CPCV during the winter approaching March parallels the
approach of the vernal equinox and peak geomagnetic disturbance (the solar
wind again) . This tendency is not present to the same degree at all during
the southern hemisphere winter when the level of geomagnetic disturbance
(solar wind invasion) is much lower (Willett 1968).
3. The climatic patterns which typefy respective phases of the DSS
cycle are by no means always present nor do they represent averages, but
rather a higher than average frequency of occurrence or intensity. There is
a statistically significant tendency for such representative patterns to
occur on alternate years, like the drought years 34-36, 54-56, 76-78, etc.
This may be an expression of the quasi-biennial cycle, which probably is of
solar origin, but this fact requires that solar-climatic seasonal prediction
must at present, in our present lack of understanding of physical mechanisms,
be based on a selection of analog years within the prevailing DSS cycle
phase.
4. Major fluctuations of the hemispheric zonal wind system, or CPCV,
sometimes referred to as the index cycle (index of the zonal westerlies) , in
a period of one to two months, is usually superposed on the normal seasonal
sequence. Several features of this index cycle are instructive as to the
behavior of the CPCV, e.g.:
a. The sequence of change is always the same as the seasonal, i.e.,
HLZ ■* LLZ ■> zonal breakdown -* HLZ, probably to some extent an autogenetic
system, whereas the phase preference sequence of the DSS cycle (HLZ -*■ break-
down ■*> LLZ ■* HLZ) is entirely imposed on the system from outside by the
sequence of activity of the solar cycle.
b. The generation of the strongly zonal circulation, HLZ ■* LLZ, from
an initial relatively resting or chaotic state, is a slow process requiring
some weeks of undisturbed action by the radiational heat balance process,
whereas the breakdown of the strong LLZ circulation usually occurs quite
suddenly by a disturbance of the thermal, hence kinetic, symmetry of the
CPCV.
11
c. There is no tendency to conservation of angular momentum in
expansion or contraction of the CPCV, but rather the contrary, i.e., we note
at the 500-mb level (Willett 1960, for 5-day means)
1) High negative correlation, 500-mb JS/latitude
2) Very high positive correlation, as required hydrostatically ,
500-mb JS/Poleward gradient of temperature
3) Slightly negative correlation, 500-mb JS/sea level ZW
4) Predominantly negative correlation, 500-mb- JS /poleward transport
of momentum at 30° and at 50°N.
All of this indicates strongly that the CPCV in its short term fluctua-
tions is driven by the solenoid field in middle latitudes, i.e., by relative
coldness in higher latitudes, not by momentum transport from the Maxwell
cells in the lower latitudes. This probably is not true of the long term
secular fluctuations.
d. Whereas the growth and expansion of the CPCV is a gradual process
involving relative cooling of the atmosphere in the higher latitudes by
radiational processes over a period of weeks without disturbance from a quiet
sun, the breakdown of the strong LLZ circulation, the breakdown of the CPCV is
a sudden process which may be accomplished in two or three days following a
sudden outburst of solar activity, in extreme cases following strong
geomagnetic disturbance, auroral and/or ionospheric disturbance, and quite
typically a sudden stratospheric warming. The following facts suggest that
a strong solar wind impulse is the primary motivating, if not direct, cause:
1) Sudden outbreaks of a quiet sun, along with sudden stratospheric
warmings and the geomagnetic disturbance and zonal circulation breakdowns
do not occur on Min- or even Min+ phase years (Labitzke, 1964). Such
events are strongest during R and F years, particularly during R years
when periods of solar quiet and strong action alternate sharply (Willett
1968, Hanzlik 1930, 1931). Best guess is that sudden localized solar wind
penetration of the upper atmosphere, as indicated by limited zones of
auroral activity, disturbs directly the thermal, hence the isobaric,
symmetry of the CPCV.
2) Roberts (1971) and his collaborators have long pointed out that
sudden geomagnetic disturbance tends to be followed by deepening of the cold
season trough at the 300-mb level over North America with the movement inland
on the north Pacific coast of the next migratory trough. This undoubtedly is
accompanied by ridging over the Pacific Ocean to the west, though Roberts
does not state that, but this represents in the Pacific-North American sector
the expected tendency toward breakdown of the zonal circulation. Furthermore,
this phenomenon was particularly strong during the Min- -> R years in the
50 's when first discovered, and weaker during subsequent years, as might
be expected.
3) Major seasonal differences between the zonal structure of the
arctic and antarctic circumpolar circulations parallel major seasonal
differences in the pattern of geomagnetic disturbance, of auroral activity, of
atmospheric ozone and of temperature in a manner entirely consistent with a
solar wind explanation (Willett, 1968).
F - 12
MERIDIONAL PATTERNS OF CHANGE OF THE GC AND CLIMATE
3.1 Synoptic Features
In synoptic terms it is the meridional, as opposed to the zonal,
component of the GC, that controls the meridional component of the climatic
pattern, just as the zonal component of the GC controls the zonal climatic
pattern. This meridional component is seen most clearly in the upper level
trough and ridge standing (Rossby) wave pattern, which rides the JS (zonal
westerlies) of middle latitudes.
Fluctuations of this upper level wave pattern in wave length (or number) ,
amplitude and meridional orientation define the fluctuations of the
meridional component of the climatic pattern, which contribute equally with
the zonal fluctuations to short term changes of climate (months, seasons and
years), but are no part of the long term secular trends, except as they may
be evident in the superposed DSS cycle when it is particularly strong.
When the climatic pattern is strongly zonal, either HLZ or LLZ, the
wave pattern is small in amplitude and long in wavelength and the meridional
climatic pattern is weak, i.e., the east-west contrasts are small and
unimportant. However, as the wave pattern becomes larger in number and
amplitude, the east-west climatic contrasts become sharper and larger, and
the zonal weaker, i.e., the GC and climatic patterns trend from zonal to
meridional, or the zonal pressure and wind belts break down progressively
into north-south oriented cells. In the extreme case we no longer have a
zonal circulation with its west to east storm tracks in middle latitudes,
but rather a completely meridional circulation of northerly and southerly
wind currents of polar and tropical air masses and strong fixed north-south
oriented high and low pressure cells which block the normal eastward move-
ment of migratory highs and lows, the so-called blocking pattern of the GC
or climatic stress (CS) pattern of climate. This is the third basic
pattern of the GC and climate, the one into which the HLZ and LLZ patterns
break down when they become chaotic.
The climatic stress pattern is the one of greatest extremes of climate,
of much more adverse climatic conditions even than the LLZ. It is not at all
favorable to glaciation, because the tendency is to hot dry summers and cold
dry winters over continents, hence it leaves little geological record for
identification by epochs, but during historical times it has produced most
human suffering and starvation. The Little Ice Age was a period of very
benevolent climate for agriculture and many other human activities.
The location of heat and drought vs. warm and wet in summer, or severe
cold vs. warm rain in winter, depends on the meridional orientation of the
trough-ridge pattern. In the U. S. the CS pattern in summer is typically
hot-dry in the midwest, and warm-wet (tropical disturbances) on the east
coast (1934-1936, 1954-1956). In winter it is cold-dry in the midwest,
northeast storms on the east coast. A westward displacement of the pattern
has given severe cold in the far west, record floods in the Ohio-Mississippi
Valley (1936-37), and an eastward displacement record cold in the northeast
(1933-34).
F - 13
We note from Figure 2 that the cellular blocking (CS) pattern tends to
be centered squarely on the R+ phase of the DSS cycle, although such
patterns, representing the complete breakdown of the zonal patterns as
discussed in Section 1, extend their influence through the Max"1" and into the
F+ phase. But all of the disastrously severe and prolonged CS periods have
been in the R+ phase (note dates in Table 1 above in reference to Figure 2) .
This is not meant to imply that this pattern may not arise during any phase
of the DSS cycle, but merely that it develops more strongly, more frequently
and of longer duration during or close to the R phase.
Two additional synoptic features of the CS pattern, of some predictive
significance, should be noted:
1. The statistically significant tendency for the DSS cycle phase
extremes of weather to occur at two, occasionally 3-year intervals. This is
true not only of extreme climatic stress conditions, e.g., see second
paragraph , but also of HLZ or LLZ extremes. This probably is part of the
significant hemispheric tendency for climatic autocorrelations to be
negative at one year's lag and positive at two.
2. A significant tendency for the upper level standing wave pattern,
i.e., the meridional component of the climatic pattern, to shift westward,
never eastward, from the calendar season one year to the same calendar
season the next year. This progressive westward displacement of a
meridional sector of severe weather has been known to continue for as long
as five years in sequence, e.g., a very severe winter over northern Europe
1946-47, east coast of the U.S. 1947-48, central U.S. 1948-49, along and
east of our west coast 1949-50, and along an off our west coast 1950-51.
3.2 The Solar Explanation of Cellular Blocking
The sudden breakdown of a strong zonal circulation pattern into a
cellular blocking (CS) pattern is probably prognostically the most
significant large-scale long-range weather event. In Section 1 in the
discussion of the breakdown of the zonal circulation it was pointed out
how observations of Hanzlik, Duel and Duel, Willett, Labitzke and Roberts
all implicate sudden solar wind as the primary direct cause of this
phenomenon, including the sudden stratospheric warming which accompanies
major occurrences.
The alternative explanation usually proposed is that the augmented
and expanded CPCV eventually reaches a state of dynamic instability, imposed
perhaps by continental or orographic barriers, and goes to pieces, the
sudden stratospheric warming being generated dynamically, by forced
subsidence, from the kinetic energy of the CPCV. However, this explanation
offers no explanation of the following facts:
1. That sometimes a strong expanded CPCV continues undisturbed for
weeks or months, other times is quickly terminated.
14
2. That the strongest and most frequent development of cellular
blocking occurs during that phase of the DSS cycle when solar wind
disturbance (geomagnetic activity) is strongest.
3. The very high coincidence between strong blocking (including
sudden stratospheric warming) with strong bursts of solar geomagnetic
disturbance.
4. That the thermal energy represented by a major stratospheric
warming (such as that of February 1952) is several times the total KE
of the initial CPCV (Willett 1968) .
If there is any point in the whole gamut of solar climatic relationships
where solar activity can be clearly predictive of major long-range weather
trends, it is in the occasional prediction of the breakdown of a strong
zonal into a severe CS pattern. The direct asymmetric supply by the solar
wind of the thermal energy to the upper atmosphere appears to be the
essential factor.
Limitation of space precludes any further speculation as to possible
explanation of solar climatic physical linkage, but a well directed program
of research certainly can come up with some answers. In conclusion a few
suggestions are offered as to the direction that such a program should
take.
Only when we have identified the specific manifestations of variable
solar activity that affect the temperature and circulation of the atmosphere
and can explain the physical linkage by which they do it will we be in a
position to take full advantage of solar-weather or solar-climatic
relationships for operational prediction.
To accomplish this we must begin with a thorough statistical analysis
of the monthly mean departure patterns of atmospheric temperature and
pressure in relation to the monthly mean departures of a number of indices
of variable solar activity carefully selected as best representative of
each of the manifestations of variable solar activity deemed capable,
directly or indirectly, of affecting the state of the atmosphere, in order
to pinpoint those aspects of solar variation which do_ affect the atmosphere
significantly, and just where.
When the disturbing solar influences are identified to the best of our
ability, we should select specific instances of strong outburst or high
level action of each disturbing factor for a detailed synoptic analysis of
atmospheric temperature and pressure, both at the ground and as high up as
reliable observational data are obtainable, to study the time and space of
atmospheric response to each disturbing influence.
Only then will we be in best position to explain the physical linkage
from variable solar disturbance to direct or indirect atmospheric or
weather response. And only when that is done will we be able to develop
most advantageously long-range weather prediction models.
F - 15
REFERENCES
Bruckner, E. (1890): Klima schwankungen seit 1700. Geographlsche
Abhandlungen, Bd. IV, Heft 2, 1890 325 pp.
Bryson, R. A. (1974): A perspective on climatic change. Science 184
(4138): 753-760.
Duell, B. and Duell, G. (1948): The behavior of barometric pressure during
and after solar particle invasions and solar ultraviolet invasions.
Smithsonian Miscellaneous Collection, Vol. 110, No. 8, 34 pp.
Eddy, J. A. (1975): A new look at solar-terrestrial relationships. High
Altitude Observatory, NCAR, Boulder, Co. 80303.
Feynman, J. and Crooker, N. U. (1978): The solar wind at the turn of the
century. Nature, Vol. 275, October 19, 1978, p. 626.
Hanzlik, S. (1930, 1931): Der Luf tdruckef fekt der Sonnenf leckenperiode.
Mitteilung I and Mitteilung II, V28 and V29 , Gerlands Beitrager zur
Geophysik, pp. 114-125 and pp. 138-55.
Labitzke, K. (1964): On the mutual relation between stratosphere and
troposphere during periods of stratospheric warmings in winter. Jour.
Appl. Meteor. , 4, pp. 91-99.
Rasool, S. I. (1964): The relationship of total atmospheric ozone to the
sunspot cycle. J. Geophys. Res. , Vol 67, pp. 661-670.
Roberts, W. D. and Olson, R. H. (1971): Study of lower stratospheric
circulation over North America following geomagnetic disturbances.
Procedings of the IUGG Symposium, Solar Corpuscular Effects on the
Troposphere and Stratosphere, Moscow, August 1971.
Sleeper, H. P. Jr. (1972): Planetary resonances, bi-stable oscillation
modes, and solar activity cycles. NASA Contractor Report - 2035,
prepared by Northrop Service, Inc., Huntsville, Ala. 35807.
Willett, H. C. (1949): Solar variability as a factor influctuations of
climate during geological time, from Glaciers and Climate. Geografiska
Annaler, 1949 H 1-2, Stockholm, pp. 295-315.
Willett, H. C. (1950): Temperature trends of the past century. Centennial
Proc. Roy. Meteor. Soc. , London, 1950.
Willett, H. C. (1951): Extrapolation of sunspot-climate relationships.
Journal of Meteorology, 8 (1), February, 1951.
Willett, H. C. (1955): Hurricanes of the Gulf and Atlantic coast of the
United States. A report prepared for the Interregional Insurance
Conference of New York, 1955, 63 pp.
16
REFERENCES (Continued)
Willett, H. C. (1960a): The statistical behavior of the general circulation
of the northern hemisphere, October 1945 - March 1952. Scientific
Report of the U. S. Weather Bureau - MIT Extended Forecasting Project,
Cambridge, Mass., September 1, 1960.
Willett, H. C. and Prohaska, J. T. (1960b): Long-term indices of solar
activity. Scientific Report No. 1, NSF Grant 5931, September 30,
1960, 39 pp.
Willett, H. C. (1965a): Solar-climatic relationships in the light of
standardized climatic data. Jour, of the Atmos . Sciences, Vol. 22
No. 2, pp. 120-136, March 1965.
Willett, H. C. and Prohaska, J. T. (1965b): Further evidence of sunspot-
ozone relationships. Jour, of Atmos. Sci., Vol. 22, No. 5,
September 1965, pp. 493-497.
Willett, H. C. (1968): Remarks on the seasonal changes of temperature and
of ozone in the arctic and the antarctic stratospheres. Jour. Atmos. Sci,
Vol. 25, No. 3, May 1968, pp. 341-360.
Willett, H. C. and Prohaska, J. T. (1977): Patterns, possible causes
and predictive significance of recent climatic trends of the northern
hemisphere. Solar Climatic Research Institute, Inc.,
October 1977.
Willett, H. C. (1978): Prediction of climatic trends. Solar Climatic
Research Institute, Inc., Cambridge, Mass., January 1978.
F - 17
WEATHER AND CLIMATE PREDICTIONS IN THE NORTHERN HEMISPHERE
BASED ON SOLAR - TERRESTRIAL RELATIONS
V. Bucha
Geophysical Institute, CSAS
141 31 Praha 4, Bocni II, Czechoslovakia
Weather forecasts for periods of 14 - 28 days, particularly as re-
gards predicting increased or decreased temperatures, sudden
penetrations of Arctic air into Europe, occurrence of more sub -
stantial precipitation, generation of zonal flow and enhanced cy-
clogenesis in the region of the Atlantic, in Europe and part of
North America, may be made by applying the proposed mechanism of
relations between processes on the Sun, variations of geomagnetic
activity and the change in distribution of temperature and pres -
sure fields in the auroral oval and the north polar cap (Bucha
1976 a,b, 1977, 1978, 1979).
1. INTRODUCTION
The process of forecasting itself will be demonstrated on the pos -
sible mechanism of solar-terrestrial relations and on the development of
meteorological situations in the Northern Hemisphere in the winter of
1974-75, beginning with the processes on the Sun and ending with a marked
increase of temperature in Central Europe, which was reflected as the final
consequence of the sequence of events that took place. Similar regularit -
ies will be demonstrated not only on six examples from 1974-75, but also on
others, which likewise occurred in the winter of 1975-76, 1976-77 (four
cases) and 1962-63 (six cases). An example of the forecast is given in the
chapter 5«
The probable causes of long-range changes of climate will also be
given, as well as an outline of the procedure for estimating the develop -
ment of the climate from the determined relations as regards changes over
an interval of 1 to 10^ years, using the proposed hypothesis of the causes
of alternation of periods of several years, climatically favourable and un-
favourable, cold and warm winters in Europe and Alaska, the occurrence of
minor glacial periods, the generation of glaciation and origin of inter -
glacial periods.
2. ASSOCIATIONS BETWEEN GEOMAGNETIC AND METEOROLOGICAL PROCESSES,
MECHANISM OF SOLAR -TERRESTRIAL RELATIONS
The comparison of certain changes of climate and temperature in the
interval 12 to 10 thousand years age (when the last period of glaciation
terminated) with the marked changes in the positions of the geomagnetic
pole, which had moved from the Pacific to the North American continent,
displays striking agreement (Fig. 1) (Bucha 1976a, 1977b). It was first
necessary to investigate whether there is an association "between the posit-
ion of the north geomagnetic pole (centre of the auroral oval) and its role
in forming the climate and weather. As regards the short-term changes, we
found a nearly unique dependence between the C^-indices, characterizing
geomagnetic activity, and the temperature variations (averages for the four
winter months) in Prague over the last 25 years (Fig. 2). After a sudden
increase in geomagnetic activity (indicating the corpuscular radiation),
represented by the daily values of the Kp-indices, we observe a relatively
sudden decrease of atmospheric pressure over the geomagnetic pole or in its
neighbourhood at the 500 mb "level, particularly during winter (Fig. 3a, b -
12 cases, Bucha 1976a).
If we look at the graphs representing gross agricultural production
in some countries (Figs. 4abc), in years when an increased level of geo -
magnetic activity was recorded in the month of May (representing the main
critical period for the growth of cereals in Central Europe and Canada),
the gross agricultural production will be seen to be higher on the average
(e.g. in 1956-60, 1967-68, 1973-74). On the other hand, when the geomagne-
tic activity was low, there was a pronounced decrease in production (e.g.
in 1954, 1962-65, 1970, 1972) (Bucha 1976b) (Fig.4abc). For Czechoslovakia
a correlation coefficient was found 0.78.
As implied by the results of spectral analysis, applied to a set of
diurnal data for a 4-year period (1962-65), Fig. 5a displays statistically
significant spectral density periods of 13.5, 9 and 6.7 days on the spect-
ral curve of both, the geomagnetic activity represented by Kp-indices and
atmospheric pressure over the geomagnetic pole ; this proves the relation
between the periodicities, particularly at the time of solar minimum (Bucha
1976b). As an other example we investigated the positive correlations
between the increase of geomagnetic activity and the decrease of pressure
over the geomagnetic pole ; during the period of November 1962 - February
1963 (five-day gliding average), a correlation coefficient was found 0.56
under a time shift 2 days (Bucha 1978) (Fig. 5b).
The results of studying the relations between geomagnetic activity
(intensity of corpuscular radiation) and the changes in atmospheric circu -
lation have indicated a positive dependence and enable a mechanism to be
proposed, which would contribute to the elucidation of the causes of marked
changes of the meteorological parameters, particularly the temperature
(Fig. 5c), pressure and air flow in the region of the auroral oval, over the
geomagnetic pole and over the most of the Northern Hemisphere (Bucha 1976-
1979).
F - 19
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F - 20
The solar-energy flux for meteorological phenomena is P_ =<7TrTT,F(l-A) =
8.9 x 10 W, if we assume the earth to have an albedo A = 0.5, rE is the
radius of the earth, F is the solar constant (Dessler 1974). The solar-
wind energy flux strikes the geomagnetic field with a total energy flux Ps,
but only less than 1% of it penetrates the geomagnetic field. Then we find
that this value of corpuscular and magnetic energy flux
- -^r2(l^ . B
MN2 ' S Z(UJ
-2 10
) V0 x 10 = 5 x 10 W , where r„
S M
is the radius
of the magnetosphere, <? is the mass density of the solar wind, 1 is
its velocity, /w0 is the permeability, and B is the strength of the inter-
planetary magnetic field. The available corpuscular energy flux is less
than one millionth of the solar-electromagnetic energy flux absorbed by the
earth.
During an intense magnetic storm, however, the corpuscular energy
flux could increase to p = 10l2 -~ lO1* W, which might be enough to use
C \ IuclX )
x/Cp
40
20
0
gpdkm.
480 .
500 .
520
540
A^iw^ih
t
+ 6
+ 4
f) -
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-8
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0-
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a
Figure 3a
XI.
1974
XII.
•+-
1975
IV.
3b
) Changes of the diurnal values of geomagnetic activity, represent-
ed by the sums of Kp-indices, daily values of the atmospheric
pressure at the 500 mb level over the geomagnetic pole and of
temperature deviations from the normal in Prague for the period
Oct .1974-April 1975. The arrows indicate the correlation and the
time lag between the increase of the Kp-indices, decrease of the
pressure over the geomagnetic pole and the increase of temperature
in Prague.
) Changes for the period 0ct.l962-March 1963 ; refer to text in
Fi-g.3a.
F - 21
this energy as a trigger (Dessler 1974), mainly for the winter hemisphere,
where Pg^- might drop to 6 x 1C)15 w. According to Roberts and Olsson (1973)
the energy of a typical rotating system of air U = 5.3 x lO-^J for the
angular velocity w = 6 x 10"-5 rad/s is comparable to the energy of a magnet-
ic storm. Thus there appears to be enough power within the magnetosphere to
cause such changes in vorticity of the lower atmosphere if the power can be
directed and coupled effectively. Let us look for the coupling mechanism
(Bucha 1977, 1979).
At the time of occurrence of magnetospheric sub-storms several paral-
lel electric currents, iq4 - 10^ A in intensity, may be generated in the
region of the auroral oval (Bostrom 1964)
The electric conductivity in the
1920
Figure 4a',
1940
1945
1950
1955
1960
1925 1930 1935
Dependence of the gross agricultural production in Czechoslova-
kia on geomagnetic activity. Curve a represents the geomagnetic
activity in May, curve b the actual gross agricultural pro -
duction, curve c the average gross agricultural production,
curve d the deviation of the gross agricultural production
from the average. Correlation coefficient 0.78. B. Dependence
of the average grain yields on geomagnetic activity in the FRG.
C. Dependence of average grain yields on geomagnetic, activity
(curve a) in Czechoslovakia (curve b) and Canada (curve c).
F - 22
20.69
V^AJ^j^<JM^V^^
Figure 5a.
Spectral function
(maximum entropy) of
geomagnetic activity
^Kn ' °^ ^e 3-'^mo ~
spheric pressure over
the geomagnetic pole
at sealevel (Mp_n_pL^
and at the 500 mb
level (Mp_500-PL)
for the period 1962-
65. The most pro -
nounced coinciding
maximum was found
for a period of 13.5
days and is evidence
of the relation
between geomagnetic
activity and atmo -
spheric pressure
over the geomagnetic
pole.
10M
6.85 T(DAYS)
106A
auroral oval is markedly increased (by as much as 5 orders of magnitude)
(Akasofu 1968) which enables Hall and Pederson currents to be generated.
Let us now speculate what the increase of temperature will be inside the
auroral oval, as a result of the energy dissipation due to Ohmic losses. The
overall energy in the centre of the oval generated as a result of the
electric currents flowing within the oval is yielded by the integration^
(Bucha 1977). Under the assumption that the maximum currents of
are considered, we would obtain a temperature increase in the centre of the
auroral zone, i.e. over the geomagnetic pole, of 13°C, which corresponds to
the anomalous temperatures actually observer! at the Earth s surface in the
region being considered during the geomagnetic storm (see four cases in
Fig. 6 and eight cases in Figs. 7-9). As a result of this a low pressure
area is generated over the geomagnetic pole and this, as implied by our
positive correlations (Figs. 5a,b,c) affects the atmospheric circulation
markedly. Even if the initial warming wereO.5 - 3°C only (during a less
intensive geomagnetic storm), it seems to represent the first trigger enab-
ling a rapid penetration of the warm air from the oceans into the auroral
belt as an after-efect (see Figs. 10a, b and Bucha 1977, 1979).
F - 23
Due to the energy of air masses coming from the Atlantic and Pacific
Oceans to the north, the increase in energy of rotation in the cyclone over
the polar cap (close to the geomagnetic pole) in 24 hours is 101' - 101" J.
Thus there appears to be enough coupling force to set the whole process in
the lower atmosphere in motion, starting in the formation of the cyclone
over the geomagnetic pole as a second trigger modifying the direction of the
air flow across the Atlantic to Europe (see Figs. 10a, b and twelve cases in
Figs. 3a, b). As an after-effect seven cases of a sudden stratospheric warm-
ing were observed (see Figs. 6 and 7).
3. THE SEQUENCE OF PHENOMENA AS A BASIS FOR PREDICTION TECHNIQUE
Relatively unstable active regions, in particular variable filaments
occur at the centre of the solar disc just before the geomagnetic activity
increases (Fig. 6a, b). A marked increase in corpuscular radiation contribu-
tes to the generation of electric currents with intensities of as much as
10° A in the auroral region (Fig. 6c). This results in a considerable en-
hancement of geomagnetic activity (characterized by K- indices), as could
have been observed, e.g., in October, November and December 1974 (Fig.6d).
These severe geomagnetic storms result in sudden changes of the temperature
in the auroral oval, as implied by meteorological observations at altitudes
of up to 24 km (Fig.6d). Between 24 and 11 km (at the 30 to 200 mb levels)
a decrease of average temperatures is observed (Fig.6d) in the region of
Figure 5b. Correlation between increased geomagnetic activity (■
•)
and decrease of atmospheric pressure over the geomagnetic pole
at the 500 mb level (----) and at sea level ( ) for
the interval 1 Nov#1962 to 28 Feb. 1963, the geomagnetic activity
preceding the pressure data by 2 days. Correlation coefficient
0.56.
F - 2k
VI ' VII ' VIII ' IX
1975
Figure 5c. Geomagnetic activity Z KL (1975-curve a), reduced corpuscular
energy flux acting on the temperature changes in winter consider-
ably (2K_re - curve b) , temperatures along the auroral oval -
north of Siberia, North America (averages from eight observator-
ies marked O - curve c), wind velocity (averages from eleven
observatories in Europe marked • - curve d) , amplitudes of micro-
seismic activity (NS component) at the observatory Pruhonice near
t*@cL
Praque (curve e). Correlation coefficient between 2 IC and
At°C (curves b and c) is 0.65 (five-day gliding average - time
shift of 4 days), between curves d and e 0.70, significance
level 0.1 % .
F - 25
7X1 1071
Figure 6a) Occurrence of unstable active region at the solar disc centre and
of a filament to the left of the disc centre on Nov«7.1974, pre -
ceding a marked increase in geomagnetic activity, b) Schematic
representation of coronal flow from unstable active region,
c) Equivalent current system for an intense polar magnetospheric
substorm. d) Geomagnetic activity (K„), temperature changes in
the auroral oval (observatory 78°N , 60°E-left-hand side), over
the geomagnetic pole (right-hand side, where the sudden strato -
spheric warming is observed) and distribution of anomalous tempe-
ratures at sea level during the geomagnetic storm (Novo9,1974 -
in the middle) .
F - 26
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the Arctic Ocean (north of Siberia - observatory 78 N , 60 E in the auroral
oval), whereas at an altitude of 5 km (500 mb) and on the Earth s surface
along the auroral oval temperature usually suddenly increases with values
exceeding the standard at the Earth s surface by as much as 30°C (Figs. 5c, 6d)
The following hypothesis can be offered to explain these observations (Bucha
1978) : as a result of the marked heating at altitudes of around 100 km in
the auroral oval, the velocities of the particles, propagating towards the
Earth and concentrated into the auroral oval, increase ; here adiabatic ex -
pansion of the rare medium takes place and this leads to the generation of
planetary pressure waves and to their penetration through the auroral oval
29
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30
into the troposphere (this is reflected in the increase or decrease of
temperatures observed at altitudes of 24 - 11 km, ref. Fig. 6d and 7.)
At altitudes below 6 km a direct transformation of kinetic into thermal
energy apparently takes place as a result of the oscillations and collisio-
nal excitation of molecules in substantially denser air layers due to the
planetary wave, propagating vertically downwards. This in turn leads to a
marked warming of the ground layers of the atmosphere along the auroral oval,
at first by between 3 - 10°C causing an intensified cyclogenesis which
brings warm air masses to the north and leads to an additional warming up to
30°C (Figs.6d,7 - left-hand side). This marked increase in temperature can
be observed especially in winter, whereas in summer it only represents one
tenth (aproximately 3°C) (Fig. 11). This follows from the ratio between the
magnitude of the overall solar energy flux in the Northern Hemisphere in
winter (6 x 10 -^W) and from the corpuscular energy flux during a geomagnetic
storm (as much as 10 ^W) , which amounts to about 10 : 1 (Dessler 1974, Bucha
1977a, 1978). The mentioned temperature manifestation in the auroral oval
(Figs. 6-9) is considerably smaller in summer, because the solar energy flux
(9 x 10 W) in summer is more than 100 times the corpuscular energy flux
(Fig.5c-curve a). Then the ratio of the corpuscular energy flux in summer
acting on the atmospheric circulation (Figs. 6-10) to the energy flux in the
winter period is one tenth as indicated by Kp,r in Fig. 5c (curve b).
A positive correlation between the corpuscular radiation indicated by geo-
magnetic activity and the temperature in the auroral oval (Fig. 5c - curve c)
was found (correlation coefficient 0.65). A correlation coefficient 0,70
shows a very close dependence of microseismic activity in Central Europe
sea,
level
Fig. 10b. The penetration of low-pressure areas from the geomagnetic pole to
the south between Greenland and Canada (Nov. 18, 1974) and across
the Atlantic towards SE (Nov. 22) as far. as Europe (Nov. 25),
resulting in a marked increase of temperatures in Europe (see
Figs. 3a, b).
F - 31
(curve e) on the wind velocity (curve d - Fig. 5c, bottom). The increase in
temperature over the geomagnetic pole lagged by 2 - 5 days and due to the
cyclonal activity the masses of warm air penetrate gradually to higher
layers and a sudden stratospheric warming can take place (Fig.6d,7 - right-
hand side - seven cases).
In order to check that the mentioned occurrences of ascending currents
(responsible for the gradual warming of the region around the geomagnetic
pole upwards into higher levels - Fig. 12 - several days after the increase
in geomagnetic activity) were not singular, we compared the variations of
I. II. III. IV. V. VI. VII. VIII. IX. X. XI XII
1974
Figure 11. Geomagnetic activity (Kp) and temperature changes at the obser -
vatories in the auroral oval (north of Siberia) showing expres -
sive fluctuations of temperature in winter (up to 30°C) whereas
in summer the temperature fluctuates by 3 - 5°C only.
F - 32
geomagnetic activity (£Kp) with the variations of temperature at levels
between 3 to 9 km, as observed at the Soviet drifting observatory SP-7
(top of Fig.12) and at the American observatory Resolute (bottom of Fig. 12).
The marked increase in temperature along the auroral oval can be
observed during a geomagnetic storm (Fig. 13a) ; in case the geomagnetic
activity is low, the increase of temperature is not observed or it does
not follow the inexpressive geomagnetic storm immediately (Fig. 13b).
The effect of the sudden increase of the corpuscular radiation can
be observed in the overall development of the situations in the Northern
Hemisphere (Fig. 8-10). At the time of increased geomagnetic activity an
expressive increase in temperature can be observed in the region of the
auroral oval (Nov. 9-11, 1974, Fig. 8); similar six cases (Fig. 9) were observ-
ed after the increase in geomagnetic activity ; thus it can be shown that
mainly in winter practically each stronger geomagnetic storm causes a
similar increase in temperature and a similar distribution of this positive
temperature effect in the region of the auroral oval.
The efect of the sudden increase of the corpuscular radiation after
a longer period of geomagnetic calm can be observed in the overall develop-
ment of the situations in the Northern Hemisphere. In Fig. 8. which repre-
sents an anomalous distribution of temperature in the Northern Hemisphere
(differences between the actual November temperatures and long-range tempe-
rature averages in November) we observe an irregular distribution of tempe-
rature anomalies at the time of low geomagnetic activity (Nov. 7, 1974) ;
On Nov. 8, i.e. on the day the geomagnetic storm commenced, there appears a
band of high temperatures in the regions north of Siberia, which increase
sharply within the next few days (Nov. 9 - 11) to as much as 20°C above the
standard value.
The warming takes place simultaneously along the whole auroral oval
(Figs. 6-9), however, particularly in the regions north of Siberia and in
Canada, where the relatively low tropospheric temperatures enable the pla -
netary wave, propagating into the troposphere as a result of corpuscular
radiation, to penetrate more easily. Within the next few days (between Nov.
13 and 17) the temperatures in the auroral oval decreased gradually and the
areas of increased temperatures moved towards the geomagnetic pole, where
they culminated between Nov. 17 and 20 (the temperature increase over the
magnetic pole amounted to 20°C with gradual penetration into the higher
levels, or even into the stratosphere, Figs.6d and 7).
The consequences of the sudden marked increase in surface temperatu-
res in the region of the auroral oval are manifested with a lag of 1 - 2
days also in considerable changes of the pressure situations in the Northern
Hemisphere (Fig. 10a). We again employed anomalous values for the distribut-
ion of atmospheric pressure (by subtracting the actual values from the Nov-
ember average), because they provide a much more lucid idea of the events
under way than the actual distribution of pressure, the constant effects of
the continents and oceans and the dependence on geographic latitude being
eliminated from them to a considerable extent. On Nov. 7, 1974, prior to
the beginning of the geomagnetic storm, the predominating well-known cy -
clones (Icelandic, Aleutian) were observed over the Atlantic, the Pacific
F - 33
2K
1958 1959
Figure 12. Comparison of temperature variations at levels between 3 and 9 km
(height-section of temperature) for the interval October 1957 -
March 1958 at the Soviet drifting observatory SP-7 (86°N, 180°E)
(at the top) with the changes of geomagnetic activity, X Kp >
shifted in time so that they precede the temperature changes by
9 days. Very similar periods of changes of the two parameters and
identity between the increased values of geomagnetic activity and
temperature can be observed. Comparison of temperature changes at
levels between 1 and 6 km (height-section of temperature) for the
interval October 1958 to February 1959 at the American observatory
Resolute (74-5°N, 80°W) (at the bottom) with changes of the geo-
magnetic activity IL . The increased temperatures -correspond
to the increased ZlC-values displaced by 3 days and vice versa.
F - 34
and partly over the North American continent, and a high pressure area over
the whole Eurasian continent. This pattern is frequent in winter under low
geomagnetic activity. On Nov. 9-12 a marked increase in geomagnetic activity
was observed and, as its consequence, a marked increase in temperature in
the region of the auroral oval, in the Arctic Ocean and Canada (Fig. 8).
This immediately resulted in a sudden and expressive intensification of
cyclogenesis outside the auroral oval, simultaneously in the Atlantic and
Pacific (Nov. 10 - Fig. 10a). Very active cyclones were generated here and
moved towards the North-East. The predominating Icelandic low and an inten-
sive cyclone, developing west of Scotland (Nov. 13-15 - Fig. 10a) moved re -
latively rapidly to the NE into the Arctic Ocean, into the areas where the
marked temperature increase had occurred (to the north of Siberia - Fig. 8).
Also the Aleutian low moved across Canada to the NE (Fig. 10a).
The air ascending to higher levels and towards the centre, the geo-
magnetic pole, allowed for a more intensive penetration of the warm masses
from the south (Nov. 12) ; this is also the reason why the low - pressure
XI.
XI.
ZKp
40
20-
sea level
y=77oN-10
A=70°E
y=80°N
*=60°E
1974
ZKp
sea level
T°C
<f=80°N'
A=95°E
-30-
</>=77on-10
A=70°E
<f=80°N
A=60°E
-10-
-30
XI.
XII.
1964
Figure 13. Positive correlation between high geomagnetic activity (Oct.-
Dec.1974) and immediate warmings at three observatories north of
Siberia, in the auroral oval (left-hand side). Low geomagnetic
activity (Oct .-Dec. 1964) is not followed by any expressive
temperature effect (right-hand side).
35
formations move towards the regions north of Siberia (Nov. 14) and of
Canada, and gradually cover the whole polar cap (Nov. 17-18 - Figs. 10a, b)
in a prevailing poleward flow.
This development of the pressure situations is at first mainly re -
fleeted in the ground layers (Fig. 10a). In the course of this process a
flow of warm air enters this level from the West and East Atlantic, which
takes over the main function of supplying warm air to the cyclone over the
geomagnetic pole in this phase (Nov. 18 - Fig. 10b). The air flow from the
Pacific along East Asia across Japan towards the NE and further across
Alaska and Canada is also directed there. In thus contributes to the creat-
ion of a high cyclone over the geomagnetic pole, which is reflected in the
gradual temperature increase at higher levels and, in winter, even by a
sudden stratospheric warming (Figs. 6d, 7, 12, 14, 3a, b, 5c).
repres
regard
12.XIL197A
This cyclone over the geomagnetic pole, or in its neighbourhood,
ents the main triggering mechanism in its further development with
to affecting fu-rther the build - up of atmospheric circulation over
the Northern Hemisphere and leading
to gradual changes of the meridional
flow into zonal. Masses of relative-
ly warmer air from both oceans are
concentrating into the cyclone over
the geomagnetic pole and leaving it
at higher levels. As the process
develops, they push the Azores high
to the south, penetrate along the
west coast of Greenland to the south
and move to the SE towards Europe, as
indicated by the growing salient of
low pressure between Greenland and
Canada (Fig. 10b - Nov. 18, 22, 25,1974).
This stops the flow of warm air from
the Azores high to the north ; the
warm flow (cyclones) proceeds from
the Caribbean directly to the east,
joins the lows, proceeding from the
geomagnetic pole to the SSE (Nov. 18-
22 - Fig. 4) and, after they have pe-
netrated to Europe, we first observe
Figure 14.
Origin of regions of increased tempe-
ratures (top) of increased cyclogenesis
along the auroral oval at sea level
(middle) during the geomagnetic storm
and their transport to the region of
the geomagnetic pole where a central
cyclone is generated over the geo -
magnetic pole ( #■ ) at the 500 mb
level (Dec. 11-12, bottom).
F - 36
a decrease of pressure and then a marked increase of temperature by as much
as 12°C (e.g., on Dec. 3-9, 1974 - Figs 3a, 6, 8, in winter 1975-76, 1976-77
Fig. 7, or several times in the winter of 1962-63 - Fig. 3b). The marked de-
crease in the level of activity which follows the magnetic storm is reflect-
ed in Europe about 14 - 20 days later by the sudden penetration of Arctic
air and an expressive drop in temperature in Central Europe after the cy -
clonal formations have passed over and before the high pressure has expand-
ed into Europe (Figs. 3a, 3b).
We have observed similar connections in more than ten cases investi-
gated. However, the dependence is not always definitive. If several,
particularly reccurent storms of several days duration follow one another,
alternating with shorter calm intervals of a few days, it may happen that
one cycle, lasting approximately 15 days, may overlap at a certain phase
with a newly originating cycle, beginning with the penetration of the plane-
tary pressure wave in the auroral oval into the troposphere (Fig.6d) and
ending with the penetration of the low from the region of the geomagnetic
pole into Europe (Figs. 10a, b, 3a, b).
Under low geomagnetic activity high pressure may be, as shown in
Fig. 4 in Bucha 1976b, generated over the geomagnetic pole, which,' together
with an extensive high pressure area over the Atlantic and possibly over
1940
1960
1976
Figure 15. Correlation of geomagnetic activity (C^-indices, curve a)
and the temperature in Prague (curve b) and Matanuska (Alaska -
curve c) for two months December - January (mean values) and
the period 1897 - 1976. Increased geomagnetic activity and
temperatures in Prague correspond to decreased temperatures in
the region of Alaska (reversed correlation).
F - 37
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North America, will hinder the penetration of cyclonal formations from the
Caribbean to the NE, which is relatively slow. A typical example at the
time of low geomagnetic activity is the development of the atmospheric
disturbance over the Gulf of Mexico on June 18, 1972 (hurricane Agnes)
(Bucha 1976b). The low pressure region was blocked from the NE and this
resulted in extensive floods and damage in the eastern part of North Ame -
rica. On the other hand the zonal flow has not penetrated into Central
and Eastern Europe which was associated with long lasting draughts, e.g.,
in the summer of 1972.
10 -20° 0° *20°^0°*60° -6 -U -2 0*2
0-
i ■ i ' i i — i — i j. i
2-
4- ■
6- ■
8- ■
10-
12 -
H -
16 - ■
i
Figure 17. A) Variations of the geomagnetic dip I in Europe, on the left
(Bucha 1976a, 1977a). Changes of air temperature in mid-
latitudes baser" on paleobotanic data (Fairbridge 1967), in the
middle. Temperature variations in the Eastern Alps (Patzelt,
Bortenschlager 1976) on the right.
B) Schematic expression of the low pressure area which is
formed as a result of the processes taking place over the polar
cap. 7^ denotes the mean position of the geomagnetic pole
which we investigated paleomagnetically : a) 0-3 for the last
3 000 years, b) 6-8-10 for the interval between 5 and 10
thousand years ago, c) 11-18 thousand years ago. The arrows
indicate prevailing wind directions.
39
4. LONG - TERM CHANGES OF CLIMATE
As can be seen from the pattern of temperature variations in Central
Europe and Alaska for the period 1918 - I960 (averages of the months De -
cember and January - Fig. 15), decreased temperatures in Alaska correspond
to increased temperatures in Central Europe and vice versa. This can be
interpreted as follows : at the time of enhanced geomagnetic activity a cy -
clone is generated over the geomagnetic pole (Fig. 14) ; it gradually ex -
pands over the whole of the North Atlantic preventing the cold masses of
air from the Arctic from penetrating into Europe - zonal flow predominates,
characterized by an increase in temperatures in Europe. Consequently, the
flow of warm air from the Pacific to the North via Alaska is inexpressive -
Alaska experiences subnormal temperatures.
After the geomagnetic disturbance is terminated, and zero or very
low geomagnetic activity is in evidence, the cyclones along the auroral oval
and over the geomagnetic pole decay. This change may result in the warm
air flowing from the Pacific via Alaska to the North and in the cold Arctic
air which penetrates at the rear of the cyclonal region relatively easily
via Scandinavia to the south. This can explain the increased temperatures
over Alaska and, simultaneously, a temperature decrease in Europe (Fig. 15).
The above indicates that changes of climate and weather seem to be
affected by changes in the corpuscular radiation (indicated by geomagnetic
activity) and by changes in the positions of the geomagnetic pole (Fig.l,
16, 17). Higher inclinations in Europe correspond to warmer climate and
vice versa.
It is known that the last interglacial period set on relatively sud-
denly, approximately 10 500 years ago, and that it relieved the last glacial
period in Europe and North America.
As given in Fig. 1 the geomagnetic pole together with the low -
pressure area were according to paleomagnetic data (Bucha 1976a) located in
the Pacific 11 - 16 thousand years ago where the zonal flow was intensified ;
Europe and eastern part of North America wereo under the influence of the
cold northern flow (Fig. 17). This could explain why these two continents
were subject to glaciation. As opposed to the above, a relatively sudden
change in climate took place in Europe and North America, for which period
we found considerable change in the position of the north geomagnetic pole
which moved from the Pacific to North America (Fig.l) (Bucha, 1976a, 1977) ;
the climate changed to a very warm interglacial period.
In accordance with the approach and receding of the geomagnetic pole
relative to Europe as well as with higher or lower geomagnetic activity
the temperatures increased and decreased which seems to be the main cause
of warmer or cooler ("minor" glaciation) periods (Fig. 17) (Bucha 1977).
^0
5. EXAMPLE OF USING THE HYPOTHESIS EXPLAINING THE SEQUENCE OF
SOLAR-TERRESTRIAL-METEOROLOGICAL RELATIONS TO PRODUCE A 28-DAY
FORECAST
If unstable active regions occur at the centre of the solar uisc
(Nov. 7, 1974 - Fig. 6a, b), a marked increase in geomagnetic activity occurs
24 to 36 hours later (Nov. 8 - 12 - Fig.6d). As follows from the sequence
of events, mentioned in the previous section and observed in 6 cases in
1974-75 (Fig. 3a), in 6 cases in 1962-63 (Fig. 3b) and also during the winters
of 1975-76 and 1976-77 (Fig.7), immediately after the geomagnetic activity
has increased we first observe a marked change in the temperatures at levels
between 24 km and the Earth s surface as a result of the planetary wave,
penetrating the troposphere in the auroral oval (Fig.6d). This process is
reflected in a marked increase of temperature in the auroral oval at the
Earth s surface, at first immediately by 3 to 10°C (Nov. 8) and then during
the next 2-3 days by as much as 30°C (Nov. 9-11) due to the penetration of
warm air from both oceans into the Artie regions (Fig. 8). As a result of
this increase of temperature towards the geomagnetic pole (Fig. 8, bottom)
the cyclogenesis in the auroral oval is enhanced substantially (Nov«9-16,
Fig. 10a) and zonal flow sets in over the North Atlantic along the coast
of Sweden due NE, as well as in the Pacific, over Canada due NE into the
region of the geomagnetic pole ; this causes an outflow of air masses from
the cyclone over the geomagnetic pole due south between Greenland and Cana-
da (Nov. 17, 18 - Fig. 10a) and then accross the Atlantic towards Europe
(Nov. 22-28, Fig. 10b). Here the zonal flow and penetration of a chain of
cyclones across the whole of Europe towards the NE is reflected in a marked
increase of temperatures by as much as 12°C (Dec. 3-9, Fig. 3a) at the end
frequently associated with enhanced precipitation and, after the last cy -
clone has crossed Europe, in a sudden drop of temperature as a result of
the penetration of Arctic air (Dec. 10-12). The sequence of changes of geo-
magnetic activity, pressure over the geomagnetic pole and of temperatures
in Central Europe can be seen in Fig. 3a, b. Therefore, depending on the
situation on the Sun (on Novo7, 1974) and particularly on the geomagnetic
storm of Nov. 8-12, 1974 one is able to forecast the weather in Europe as
far as Dec. 10, 1974. Fifteen other sequences, as can be seen in Figs. 3,
6-14 (Bucha, 1976a, b, 1977, 1978, 1979), were manifest in a similar way.
CONCLUSION
Wilcox et al. (1973) have presented results showing a correlation
between geomagnetic storms and winds and pressure throughs. Positive cor -
relations of geomagnetic and meteorological data (Figs. 1-3), of geomagnetic
activity and agricultural production (Fig. 4), of geomagnetic activity, tem-
perature, pressure and wind velocity were found (Bucha 1976-9) (Figs.5abc).
Further the character of the actual meteorological processes confirms the
proposed mechanism of solar-geomagnetic-meteorological relations (Fig. 5c)
and 11 cases of vertical propagation of temperature effects in the auroral
oval and 7 cases of sudden stratospheric warmings (Figs. 6, 7), 7 cases of
the warming in the auroral oval which immediately follow the increase of
corpuscular (geomagnetic) activity (Figs. 8, 9) and 12 cases of dependence
F - k\
between the changes in geomagnetic activity, decrease of atmospheric pres -
sure at the 500 mb level over the geomagnetic pole and changes in tempera -
ture in Central Europe - Figs. 3a, b). The findings indicate the feasibility
of 14 - 28 day weather predictions for Central Europe ; at the same time
the suggested relations can be utilized for studying the corpuscular (geo-
magnetic) effects on the changes in atmospheric circulation in other areas
of the Northern Hemisphere.
The seasonal predictions of winter temperatures according to the
correlations given in Fig. 2 (mild or severe winters) can be made and the
vegetation conditions for agricultural production may be tentatively pre -
dieted according to the expected geomagnetic activity in May which, accord-
ing to Fig. 4, indicates favourable (high geomagnetic activity) or less
favourable conditions (low geomagnetic activity) what concerns the prevail-
ing types of atmospheric circulation including mainly temperatures and pre-
cipitations during the main vegetation period (May to July).
REFERENCES
Akasofu, S. (1968): Polar and Magnetospheric Substorms. D.Reidel Publ.Comp.,
Dordrecht.
Bostrbm, R. (1964): A Model of the Auroral Electrojects. J.Geophys.Res. ,
69:4983.
Bucha, V. (1976a): Variations of the Geomsgnetic Field, the Climate and
Weather. Studia geoph.et geod.. , 20:149.
Bucha, V. (1976b): Changes in the Geomagnetic Field and Solar Wind-Causes
of Changes of Climate and Atmospheric Circulation. Studia geoph.et
geod. , 20:346.
Bucha, V. (1977a): Mechanism of Solar-Terrestrial Relations and Changes of
Atmospheric Circulation. Studia geoph.et geod., 21:350.
Bucha, V. (1977b): Causes of Glaciations, Climate and Weather Changes.
Pro.ject TUGS, UNESCO 73/1/24, Report No. 4. Stuttgart-Prague.
Bucha, V. (1978): Possible Mechanism of Solar-Terrestrial Relations.
Cp_ 1 1 e c t ion of Ext en ded_ Summaries of Contributions Presented at Joint
IAGA/IAMAP Assembly Seattle, Washington, IAMAP , Boulder, Colorado.
Bucha, V. (1979): Connections between Geophysical and Meteorological
Processes. Studia geoph. et geod. , 22:130.
Burlackaya, S.P. (1965): Archeomagnetizm. Nauka, Moskva
Dessler, A.J. (1974): Some Problems in Coupling Solar Activity to Meteorolo-
gical Phenomena. Symp. Possible Relationships between Solar Activity
and Meteorological Phenomena, Nov- 1973 , Nat .Aeronautics and Space Admin.
F - kl
Easterbrook, D.J., Othberg, K. (1976): Paleomagnetism of Pleistocene Sedi -
ments in the Puget Lowland. Pro.ject IUGS. UNESCO 73/1/24, Report No. 3,
Bellingham-Prague .
Eddy, J. A. (1976): The Maunder Minimum. Science. 198:824.
Fairbridge, R.W. (1967): The Encyclopedia of Atmospheric Sciences and Astro-
geology. Reinhold Publ.Corp., New York, Amst., London
Kovaceva, M. (1970): Archeomagnitnye issledovanija v NR Bolgarii. Sb. tezisov
dokl. VIII. konf. po post.geom. pol.ju i paleomagnetizmu.
Le Roy Ladurie, E. (1969): Histoire du climat depuis 1 an mil. Flammarion,
Paris.
Patzelt, G., Bortenschlager , S. (1976): Spat-und Postglacial im Otztal und
im Inntal. Fiihrer zur Exkursionstagung des IGCP Pro.jektes 73/1/24,
Stuttgart.
Roberts, W.O., Olson, R.H. (1973): New Evidence for Effects of Variable Solar
Corpuscular Emission on the Weather. Rev. of Geophys. and Space Phys. ,
11:731.
Wilcox, J.M., Scherrer, P.H. , Svalgaard, L. , Roberts, W.O. and Olsson, R.
(1973): Solar Magnetic Sector Structure : Relation to Circulation of
the Earth s Atmosphere. Science, 180:185.
Yaskawa, K. (1974): Reversals, Excursions and Secular Variations of the
Geomagnetic Field in the Brunhes Normal Polarity Epoch. Paleolimnology
of Lake Biwa and the Japanese Pleistocene, 2.
F - 43
THE EFFECTS OF CHANGING THE SOLAR CONSTANT
ON THE GENERAL CIRCULATION OF THE EARTH'S ATMOSPHERE
T. Asakura and Y. Tanaka
Longrange Forecast Division, Japan Meteorological Agency
Tokyo, Japan
Much statistical evidence of a solar-weather relationship is
not necessarily accepted as universally true due to lack of under-
standing of the physical processes of solar-weather phenomena.
This study is an attempt to clarify the physical processes in the
atmosphere caused by changes of solar constant.
1 . MODEL CALCULATION
1.1 The Model and Physical Processes Involved
The numerical model used in this study is the Statist ical -Dynamical
Model developed by Kurihara (1970, 1973), though the heating function has
been revised. Despite many restrictions in the model, Kurihara (1973)
successfully reproduced the seasonal change of the atmospheric circulation
in his ocean-covered model.
The model atmosphere is divided into two vertical layers between the
upper boundary, p=0, and the lower boundary, the earth's surface. In the
meridional direction, the atmosphere between the north and the south poles is
divided into ^8 zonal rings having the same width.
By using the zonally averaged primi t ive equations , the first law of
thermodynamics, the continuity equation, and hydrostatic assumption, we
predict zonal mean wind components and eddy kinetic energy both at 250 and
750 mb, and zonal mean temperature and heat transport at 500 mb .
Precipitation is obtained as a difference between the water-vapor supply
from the sea surface and the moisture flux divergence in an air column. The
heat balance equation is solved at the land surface and land-surface tempera-
ture is obtained to estimate the sensible heat supply.
The long-wave radiation scheme used in this model is similar to that
adopted by Smagorinsky (1963). In this study, the effects of land-sea distri-
bution are incorporated by considering the area percentages of land and sea
at each zonal ring.
The horizontal sensible heat transport is estimated using the equation
derived assuming that the heat transport by baroclinic waves is performed
only by a representative baroclinic wave determined by use of theoretical
investigations. Concerning eddy transport of momentum, an assumption was
made that the momentum flux divergence at the highest level is counterbalanced
by frictional stress between the lowermost atmospheric layer and the earth's
F - kk
surface. This model further assumes the earth's surface to be flat, thus so-
called feedback mechanism is not incorporated.
1.2 Boundary Conditions, Changes in Solar Constant, and Time Integrations
The planetary albedo is taken from the table of Smagorinsky ( 1 963 ) and
is assumed to be symmetrical with respect to the equator. Sea-surface tem-
perature and land-sea ice distributions are the same as those used in the
Mintz-Arakawa Model (Gates et al., 1971). Those boundary conditions are kept
fixed at their prescribed values throughout the time integrations.
Our preliminary run was begun with the atmosphere at rest and was con-
tinued up to the end of the second year with the seasonal march of solar inso-
lation. The land-sea ice distribution was introduced on the last day of the
preliminary run. Then the time integrations were carried out anew up to the
30th day of the fourth year.
The time integrations were made for three cases: the normal case (de-
noted as N-case hereafter) with a normal solar constant, 2.00 ly miri"; the
increased case (denoted l-case), with an increase in solar constant of 3%\ and
the decreased case (D-case) , with a decrease in solar constant of 3%. We
found that the time equilibrium was almost attained by the beginning of the
third year, so the period from January to December in the third year was
chosen for analysis. In the following, we mainly discuss the differences be-
tween N-case and D-case, namely the effect of the decrease in solar constant,
especially on the characteristics of atmospheric motion and atmospheric temp-
erature in the northern hemisphere.
According to Kondratyev (1969), a change in solar constant of about 3%
is possible. A change in solar constant itself by +3% to -3%, in this study,
may be too large; but when we consider the increase in aerosols in the atmo-
sphere, a change in direct solar radiation to the top of the troposphere of
about 3% may be possible.
2. DIABATIC HEATING AND MEAN TEMPERATURE
We first investigate the changes in heating functions, which are the
driving forces of atmospheric circulation, due to the decrease in solar con-
stant. Diabatic heating in this model is obtained as the net sum of short-
wave radiative warming, long-wave cooling, sensible heat supply from the
earth's surface, and release of condensation heat.
Figure 1(a) shows the seasonal march of monthly hemispheric averages
of diabatic heating components for N-case. Figure 1(b) then is shown for D
minus N case, that is, the changes due to the decrease in solar constant by
3%. Figure 2(a) shows the meridional distribution in these components for
N-case, while Figure 2(b) gives the differences, D minus N case. Temperature
at 500 mb is also depicted in these figures.
The precipitation seems to be influenced most by a decrease in solar con-
stant. Figure 2(b) reveals that the decrease in solar constant brings about
a large decrease in annual mean rainfall in the tropics of 6%, especially
around 13°N; on the contrary, precipitation increases in the middle latitudes.
In high latitudes around 60°N, the decrease amounts to 3%>
F - 45
(a)
(b)
i* 4
MONTH
Figure 1. (a): The seasonal march of monthly northern
hemispheric averages of diabatic heating (DIA) and its com-
ponents; sensible heat supply from the earth's surface (SENS),
short-wave radiative warming (SW) , long-wave radiative cooling
(LW) and release of condensation heat, or precipitation (PREC) ,
and temperature at level 2 (T2) for N-case .
(b) : Same as (a) except that the seasonal march of
differences between D-and N-case is shown.
Figure 1(b) shows that, in the hemispheric average, the largest decrease
appears in June, by k%, with an annual mean decrease of 2%. It is noticeable
that in figures 1(b) and 2(b) the precipitation and diabatic heating curves
run almost parallel to each other, so the change in precipitation seems to
play an important role on the change in diabatic heating. Figure 1(b) shows
F - 46
OBSERVATION T2
(a)
SON, go
(b)
7.0 . 6P .59 . ^O 30 . 20 . IP" . O
LATITUDE (deg)
Figure 2. (a): The meridional distribution of annual
latitudinal averages of diabatic heating and its components
and temperature at level 2 for N-case. (See Figure 1 for
notations) .
(b) : Same as (a) except that the distri-
bution of differences between D- and N-case is shown.
that the hemispheric averages of changes in sensible heat supply from the
earth's surface are very small; but, as is seen in Figure 2(b), they contri
bute to changes in diabatic heating in the tropics and middle latitudes.
F - kl
The hemispheric mean temperature also falls and reaches its greatest
decrease of about 0.5°C in summer, with an annual mean value of 0.4°C, as is
shown in Figure 1(b). Figure 2(b) shows that in both the tropics and polar
region, this decrease is large, while in higher latitudes the decrease is the
smallest. Concurrent with the changes in temperature, the long-wave radia-
tive cooling also weakens with a hemispheric annual mean decrease of 2%, as
shown i n Figure 1 (b) .
The change of diabatic heating in this model is equal to the net sum of
the changes in the above constituents, so the diabatic heating weakens by
about &%, with its largest value in June while the annual mean decrease is
about 1%, as is shown in Figure 1(b).
Figure 2(b) shows that the decrease in diabatic heating is most pro-
nounced in the tropics, especially around 13°N, with a minimum of 11% mainly
due to the decrease in precipitation. On the contrary, in middle latitudes
around 35°N, the warming intensifies by 8% due to the increase in precipita-
tion. So the changes in diabatic heating bring about the imbalance on the
heating field between low and middle latitudes. The contrast of heating, or
thermal gradient, weakens between low and middle latitudes while between
middle and higher latitudes, it becomes large. Thus, these imbalances must
be canceled out by means of changes in atmospheric circulation.
3. DIABATIC HEATING AMD GENERAL CIRCULATION
Next we study how the changes in diabatic heating are balanced by the
changes in atmospheric circulation. We estimate, in this model, the time
derivative of atmospheric temperature as the net sum of eddy and mean hori-
zontal sensible heat flux divergence, adiabatic heating due to eddy and mean
vertical motion, heat diffusion, and diabatic heating.
Figures 3 and k show the variations of each component mentioned above.
In Figure 3, the seasonal march of the monthly hemispheric averages of the
components for N-case and those of differences in these components between
the D- and N-cases are shown. In Figure h, similar to Figure 2, the meridio-
nal distribution of the annual latitudinal averages for N-case and those of
differences between the D- and N-cases are illustrated.
3. 1 Vert ical Motion
Figure 3(b) clearly shows that the decrease in diabatic heating is
almost compensated for by the weakening of mean upward motion, or intensifi-
cation of downward motion, so far as the hemispheric averages are concerned.
The weakening is most remarkable in June; on the average the upward motion
weakens by 15% over the year. The role of eddy vertical motion is very small
compared with that of mean motion.
Figure 4(b) clearly shows that adiabatic cooling diminishes in low lati-
tudes due to weakening in mean upward motion ; and that it counterbalances the
decrease in diabatic warming there. Around 30°N, weakening in adiabatic
warming is distinct, meaning a weakening in downward motion to. balance with
the increase in diabatic heating there. These changes in mean vertical motion
in the tropics and around 30°N imply the weakening of Hadley circulation.
F - 48
(a)
(b)
1.8
1.6
■
1.4
1.2
.
1.0
0.8
■
I OIABATIC
\ HEATING
r
0.6
0.4
0.2
0.0 •
MEAN SENSIBLE
HEAT PLUX ^
DIVERGENCE *"*.
•V «.^-^—
-0.2
C(TW)
eddy
-0.4
-0.6
C(T V )
mean
-0.8
-1.0
-1.2
J
MONTH
1
*
IT
<j j y
f £ Q
V
J>
1.0
•> O.J
-0.5-
Figure 3. (a): The seasonal march of monthly
northern hemispheric averages of energy conversion terms;
diabatic heating, mean sensible heat flux divergence,
conversion between potential and kinetic energy by eddies
(C(T 'W ■) ) , and by mean flow (C(T W )), where the notation
W means vertical P-velocity, for N-case.
(b) : Same as (a) except that the seasonal march
of differences between D- and N-case is shown.
F - 49
(a)
(b)
9q_
3 0.0
EDDY SENSIBLE HEAT
FLUX DIVERGENCE
§0 ■ 70 . <*> . 3P . 4Q , 30 , 20 . UDN . 0
LATITUDE
EDDY SENSIBLE HEAT
FLUX DIVERGENCE
K
** w 1'/
\ A*
/ V * *
7 ^0*
9 \
\ / C(T V )
*»/ mean
/ V
/ <%rl
/ i \
■ *i
• ii
7 \^
' "
DIABATIC^j^
HEATING
Figure k. (a): The meridional distribution of
annual latitudinal averages of energy conversion com-
ponents for N-case. (See Figure 3 for notations.*)
(b) : Same as (a) except that the seasonal march
of differences between D-and N-case is shown.
Around the tropics, the change in diabatic. heating is almost compensated
for by the change in mean vertical motion, but in middle and high latitudes,
the sensible heat flux also plays a part to balance with the changes in
diabatic heating.
F - 50
3.2 Horizontal Sensible Heat Flux Divergence
We see in Figure Mb) that around 25°N the cooling due to eddy sensible
heat flux divergence weakens as the solar constant decreases; this means that
the efficiency of sensible heat transport from low to middle latitudes lessens
and corresponds with a weakening in Hadley ci rculat ion. Around 40°N, the
decrease in solar constant causes an intensification in cooling by sensible
heat transport by eddies, and this compensates for the intensification of
diabatic heating due to the increase in precipitation there. Around 50°N,
the heat flux warms the region. Thus the eddies transport more sensible heat
from middle to higher latitudes due to the change in solar constant, and
therefore the Ferrel circulation intensifies.
Since we assumed that sensible heat flux at the north and south poles
is zero, the net hemispheric average in sensible heat flux divergence by mean
flow is equal to an inflow, or outflow, of sensible heat to the other hemi-
sphere. Figure 3 shows that the decrease in solar constant results in a
weakening of sensible heat inflow in summer and a weakening of outflow in
winter. This also means a weakening of hemispheric interaction due to a
weakening in Hadley circulation at both hemispheres.
3.3 Temperature and Mean Zonal Wind
Figure 2(b) shows that the decrease in solar constant causes a weakening
in barocl inici ty between low and middle latitudes and a strengthening between
high and polar latitudes. So the subtropical jet stream is weakened while
the polar jet stream is strengthened, although their positions do not change
remarkably .
SUMMARY AND DISCUSSION
Figure 5 shows our results schematically. As is seen, the decrease in
solar constant results in the following effects in the atmospheric circula-
tion:
1. Precipitation in summer decreases sharply in low latitudes, result-
ing in the weakening in diabatic warming which is balanced by a weaken-
ing of mean ascending motion in the southern branch of the Hadley cell.
Diabatic warming in middle latitudes is intensified by the
increase in precipitation and sensible heat supply from the surface. In high
latitudes around 55°N, diabatic cooling is intensified by the decrease in
precipitation and sensible heat supply. An imbalance between these two lati-
tudes is cancelled out by the enhancement of sensible heat flux in the Ferrel
circulation. Wetherald and Manabe (1975) and MacCracken and Potter (1975)
obtained similar results on the changes in precipitation.
2. Mean temperature of an air column decreases, especially in tropical
and polar regions. However, the amount of decrease is about one-tenth of
those in studies by Wetherald and Manabe (1975), MacCracken and Potter (1975),
and Budyko (1969). The discrepancy may be due to ignoring feed-back mechanism
in the present model.
F - 51
(HIGH LATITUDES) (MIDDLE LATITUDES) (LOW LATITUDES)
(-) PRECIPITATION &
SENSIBLE HEAT SUPPLY
(-0 DIABATIC COOLING
(-) T2 (the smallest)
l(+) PRECIPITATION!
(+) DIABATIC
WARMING
(-) T2 (smaller)
1
I(-t-) DIABATIC HEATING
CONTRAST
(+) ADIABATIC
WARMING
(+) SENSIBLE HEAT
TRANSPORT
(+) PERREL
CIRCULATION
(+) POLAR JET
STREAM
(-) PRECIPITATION
(-) DIABATIC
WARMING
1
(-) T2
(the largest)
:r
TTT2
CONTRAST
(-) SENSIBLE
HEAT
TRANSPORT
(PRECIPITATION &
SENSIBLE HEAT SUPPLY)
(DIABATIC HEATING)
(TEMPERATURE)
ADIABATIC
COOLING
zr
(-) HADLEY
CIRCULATION
(-) SUB
TROPICAL
JET
(GENERAL
CIRCULATION)
Figure 5. Schematic diagram of changes of components
in atmospheric circulation caused by the decrease in solar
constant. Bold-lined rectangles show intensifying (or
increasing) phenomena, while thin-lined rectangles show
weakening (or decreasing) phenomena.
3. In l-case, with an increase in solar constant, phenomena appear to
be just the reverse of those in D-case, qualitatively and quantitatively.
In this paper, special emphasis should be placed on the fact that a
change in solar constant brings about regionally and seasonally different
effects on weather, and the differences are caused by a deformation of atmo-
spheric motion. It is this deformation that makes our understanding of
solar-weather evidence more difficult.
Acknowl edgements
The authors express their hearty thanks to Dr. Y. Kurihara for giving
them his excellent model, and Dr. A. Katayama for his helpful suggestions and
discussions. They also thank the staff of Longrange Forecast Division, in
the Japan Meteorological Agency, for their encouragement through this study.
REFERENCES
Budyko, M. I. (1969): The effect of solar radiation on the climate of the
earth. Tel lus, 21:5.
F - 52
Gates, et al. (1971): A documentation of the Mintz-Arakawa two-level atmo-
spheric general circulation model.
Kurihara, Y. (1970): Stat istical -dynamical model of the general circulation
of the atmosphere. J. Atmos . Sci . , 27-
Kurihara, Y. (1973): Experiments on the seasonal variation of the general
circulation in a statistical -dynamical model. J. Atmos. Sci . , 30.
Kondratyev, Y. K. and Nikolsky, H. I. (1969): Solar radiation and solar
activity. 0_uar. Jour. Roy. Met. Soc, 96.
MacCracken, M. C. and Potter, G. L. (1975): Comparative climatic impact of
increased stratospheric aerosol loading and decreased solar constant in
a zonal climate model. Proceedings of the WMO/IAMAP Symposium on Long-
Term Climatic Fluctuation.
Smagorinsky, J. (1963): General circulation experiments with the primitive
equations, I. The basic experiment. Mon . Wea . Rev . , 91 •
Wetherald, R. T. and Manabe, S. (1975): The effects of changing the solar
constant on the climate of a general circulation model. J . Atmos . Sci . ,
32.
F - 53
METEOROLOGICAL MICROSEISMS AND SUN- WEATHER RELATIONSHIPS
Jan Lastovicka
Geophysical Institute, Czechosl. Acad. Sci.,
Bocni II, 141 31 Prague 4, Czechoslovakia
The purpose of this paper is to show the usefulness of meteorological
microseisms recorded at inland stations, inexpensive and less-known
data, in sun-weather studies and predictions. The long-term variabi-
lity of microseisms, their short-term variability, including response
to geomagnetic storms and their response to the IMF sector boundary
crossings are shown. Some possibilities of using them in a short-ran-
ge weather forecasts are also shown.
1. INTRODUCTION - MICROSEISMS
Sun-weather relationships have been studied very extensively in various ways
in recent years. The exploitation of meteorological microseisms for this purpo-
se belongs to the less-known (perhaps even generally unknown) methods used. The
purpose of the present paper is to summarize some older results of their use in
sun-weather studies, to present some new results and to point at possibilities
of exploiting them for predictions.
Besides earthquakes, the seismograph also records other motions, generally
called "seismic noise". Seismic noise in the range of periods of about 1-10 sec
is called "meteorological microseisms" (hereafter only microseisms). The micro-
seisms reach the largest amplitudes at coastal seismic stations. These microsei-
sms represent coastal effects or effects of close local sources. However, the
microseisms recorded at stations, situated well inland like Prague, are of a di-
fferent origin. Local and coastal effects are suppressed and background micro-
seisms, which are a response to changes of atmospheric pressure fields and to cy-
clonal activity over large water areas (mainly over oceans), are recorded. The
generation of microseisms is conditioned by rapid, intense changes in the pres-
sure field pattern - even large stationary cyclones do not produce microseisms
(Zatopek, 1976).
Source regions of microseisms observed at Prague (generally in Central Euro-
pe) are situated in the North Atlantic frontal zone, where the appearance of pro-
nounced cyclonic activity is always connected with a sudden enhancement of micro-
seisms. The region to the west, south-west and south of Iceland, surroundings of
the Jan Mayen Island, the area off the coast of Central Norway, the northern Nor-
wegian coast and the northern part of the Baltic Sea are these regions (Zatopek,
1964, 1976). On the other hand, there are some sourceless regions like the shal-
lows off the coast of Greenland, the North Sea, the English Channel, the Mediter-
ranean Sea, etc.
F - 5k
Meteorological microseisms, recorded at Prague, are strongly seasonally de-
pendent. They are relatively large and well-developed in winter, whereas in sum-
mer they are often hardly detectable, perhaps due to different conditions of
air-water interaction (Zatopek, 1966).
It is worth noting that the striking similarity, found in the regime of
smoothed amplitudes of Northern Hemisphere microseisms (Europe and Japan) down
to the latitudes of about 35 N, has been explained by the integral activity of
the great polar vortex in the atmosphere (Zatopek, 1975). This finding together
with the fact that the Central Europe microseisms are created in the key region
of European weather and at latitudes high enough, where the sun-weather relati-
onship is expected to be developed, indicate that it is suitable and necessary
to exploit meteorological microseisms for investigating sun-weather relations.
2. IMF AND MICROSEISMS
The interplanetary magnetic field (IMF) belongs to the important phenomena
which play a role in solar-terrestrial relationships. The relation between mic-
roseisms and the IMF sector boundary crossings and IMF radial component polari-
ty was studied by Lastovicka (1977, 1978). The results for the winter period
(November 15 - March 15) are given in Fig. 1. All the values are presented in
the form of I/I , where I is the crossing day value. The curves represent mean
values over the period 19o6-1973 (microseisms 1962-1968 - lack of data after
1968), regardless of the type of crossing. On one side of each curve the desig-
nation of the physical quantity and the scale are given, on the other side the
+/- ratio and the number of crossings, n. The +/- ratio is the ratio of the 3-
day average values observed in the away (+) sector to those in the toward (-)
sector.
The same effect of sector boundary crossings, which consists in a more or
less deep depression related to the boundary crossing, is observed in all the
three types of quantities shown in Fig. 1. The values in the toward sector are
a little higher than those in the away sector (+•/- < 1). The statistical signi-
ficance of the difference between extreme mean data points of the curves is bet-
ween 75% (1178 kHz) and 99% (VAI 12 UT). The atmospheric vorticity area index at
500 mb characterizes the state of the troposphere northwards of 10 N. The radio
-wave absorption data characterize the state of the daytime lower ionosphere
over Central Europe (GDR). The less smoothed character of the microseismic cur-
ve is due to a lower number of data used.
Lastovicka (1978) found another type of the IMF boundary crossing effect in
the IMF magnitude, Ap, cosmic rays and in the nighttime radio-wave absorption in
the lower ionosphere. It enables us to conclude that there are different types
of the IMF sector boundary crossing effect depending on the altitude and, partly,
on the phase of the day, and it represents further evidence of the usefulness of
meteorological microseisms in studying extraterrestrial influence on the weather.
The sector boundary crossing effect in microseisms is similar for +/- and
-,+ crossings in winter, but there is practically no such effect in spring and
autumn. In contrast to a very weak winter tendency to higher microseismic acti-
vity in the toward sector, a slight but non-negligible opposite tendency is ob-
served in spring and autumn (Lastovicka, 1977).
F - 55
(+A>0.98
n«26
62-68
.05-
VAI
500 nb
00 «T 0.95
C+7^)- 0.98
n= 70
245kHz
INI
1.05
1.0
(7^>097
n= 62
2775kHz
105-
10-
1.2
microseisms
-1.1
ID
(V>0.97
n =72
1.15 VAI
500il
12 UT
1.0
(+/->0J8
n-70
1.05
1178 kHz
10 ""
(+/->0.97
n-56
-3 -2 -1 0 +1 +2 +3
Fig. 1. The IMF sector boundary crossing effect in the amplitude of Prague mete-
orological microseisms, the Northern Hemisphere atmospheric vorticity area in-
dex (VAI) at the 500-mb level, and in radio-wave absorption (2775 kHz, 1178 kHz,
245 kHz) in the lower ionosphere at noon after Lastovicka (1978). +/• ••♦ the
ratio of values observed in the away (+) sector to those observed in the toward
(-) sector.
3. LONG-TERM VARIABILITY OF MICROSEISMS
The long-term variability of Prague microseisms was studied by LastoviSka
(1974), Zatopek (1975), Zatopek and Krivsky (1974) and Zatopek et al. (1976) in
relation to various phenomena associated with solar activity. They found a chain
of interrelated phenomena (in the long-term sense) beginning at the sun and en-
ding at the earth: the occurrence of solar flares, associated with type IV radio
bursts (sun) - cosmic rays (interplanetary medium variability) - Ap. (geomagnetic
field) - radio-wave absorption (lower ionosphere) - microseisms (solid earth).
56
1946J0 52 54565860626466 y*ars
0 ' — i — i — i — i — i — i — r
250
200
150
100
10.7
T
[s]
4.8
40
194850 52 54565860 62 6466 years
Fig. 2. Long-period (1948-1967) data on A = 10.7 cm solar radio flux (a), sun-
spot numbers R (a' )» cosmic ray intensity at Cheltenham (b), geomagnetic Ap in-
dices (c), LF radio-wave absorption on 272 kHz at the Pruhonice Observatory (d),
maximum smoothed microseismic amplitudes at Prague (e), mean microseismic ampli-
tudes at Prague (f), mean microseismic periods at Prague (g), and the occurren-
ce of solar flares associated with type IV radio bursts (h). After Zatopek et
al. (1976).
All these quantities together with the sunspot number R and solar radio noise
F. are given in Fig. 2. All the quantities exhibit relatively strong secon-
dary peaks in the solar cycle (1951/52, 1959/60), except R and F. Thus, those
components of solar activity, which are associated with the geomagnetic activity
(flares IV - CR - Ap) and not only with the solar wave radiation (F,R), seem to
play the major role in sun-micro seisms (weather) relations, as is expected (e.g.
57
King, 1975). As regards micro seisms, the two-peak structure is developed parti-
cularly well for their periods. The best-fit lines are: T(sec) = 0.039 Ap *
0.0015 F + 3.85, T(sec) = 0.040 Ap + 0.0011 R + 3.39; correlation coefficients:
r(T,Ap) = 0.74, r(T,R) = 0.54, r(T,F) = 0.52 (Lastovicka, 1974).
The above chain of interrelated phenomena may be extended to the circumpo-
lar vortex activity in the circumpolar pressure pattern, the variability of
which is reflected by microseisms (Zatopek, 1975). These phenomena may be lin-
ked by a chain of associated processes, beginning with a particle and plasma
cloud ejection during flares with type IV radio bursts, as suggested by Zatopek
et al. (1976). Even if the chain of interrelated phenomena is not complete and
some processes are not clarified, it is believed to provide a good initial ba-
sis for more profound studies of solar-terrestrial links.
The Prague meteorological microseisms form a long-period homogeneous se-
ries of data. As illustrated in this section, they represent a very convenient
basis for studying various long-term effects in the lower atmosphere, particu-
larly in the winter polar vortex.
4. SHORT-TERM VARIABILITY OF MICROSEISMS. PREDICTION POSSIBILITIES
The Prague microseisms are a response to the meteorological activity in
the North Atlantic frontal zone, where most of the Central Europe weather (cyc-
lones and frontal systems) is generated. Thus microseisms could be used for
short-range (several days) qualitative weather forecast in Central Europe.
The short-term variability of microseisms and some other quantities are
shown in Fig. 3 for the last quarter of 1974. The vertical lines in Fig. 3 indi-
cate individual microseismic bursts. It follows from the strong seasonal depen-
dence of microseismic amplitudes (Section l) that even weak microseismic distur-
bances in October may indicate more significant meteorological activity than
moderate or medium microseismic bursts in December.
The comparison of microseismic bursts with geomagnetic storms or activity
enhancements displays a two-peak structure of microseismic response to geomagne-
tic storms. The direct effect of a geomagnetic. storm is observed on the day of
maximum 2Kp (within an interval - 1 day], whereas the after-effect, which is
comparable in magnitude with, and may be even larger than direct effect, is
observed 2-4 days after the direct effect. The two-peak microseismic response
strongly resembles the well-known two-peak effect of magnetic storms in the LF
radio wave absorption in the midlatitude lower ionosphere. The occurrence and
time-delay of the after-effect in Prague microseisms are consistent with a large
decrease of the mean atmospheric pressure (about 10 mb) in the Iceland-Scandina-
vian region 3-5 days after strong sporadic geomagnetic bursts (Mustel et al.,
1977). It is worth noting that the vorticity area index response to geomagnetic
storms is less developed and besides a fairly sharp decrease in VAI a day or so
following geomagnetic event, a 7 day delti^-. .Lncrease of VAI seems to appear.
Only 2. Kp is presented as a characteristic of magnetic activity, because daily
values of auroral electro jet index (AE) yield the same general pattern as Kp.
A good response of the daily values of atmospheric temperature at the surf-
ace to magnetic activity was observed by Bucha (1977) for several high-latitu-
F - 58
Al/um)
EW
Al/umJ
NS
0
>
10
V
«-
_l I 1 u
• . » i
• • • ■ i V • •
.". ./
-— •» V •
"* "X
V-V.
11 21 31
October 1974
10 20
November
j i 1 1 1 ' 1 £r
30 1Q 20 30
December
10
0
»
0
-20
.-t.0
ik
.40
■20
■0
>k
.80
.40
■0
it
-U0
-0
>
10
0
Fig. 3. Day-to-day variability of the amplitude A of Prague meteorological mi-
croseisms (separately NS and EW component; data points at 00 and 12 UT; cros-
ses - long-period microsei3ms) , the Northern Hemisphere atmospheric vorticity
area index VAI at the 500-mb level, geomagnetic index £Kp, daily values of
temperature Ti at a meteorological station (80°N, 80°E), and daily values of
temperature T2 at Prague for the period October-December 1974. The VAI values
since November 20 are missing. d,a - direct effect and after-effect in micro-
seisms, respectively; ? - uncertain.
de stations in the period studied. The data of one of these stations are given
in Fig. 3 as Tx. They correlate fairly well with geomagnetic activity, but the
T^-response (an increase with increasing magnetic activity) is different in in-
dividual events. There are two enhancements of geomagnetic activity (Decbmber 3
and the strongest one of October 13), accompanied only by a "microresponse" in
the direct effect in microseisms. These two events display no effect in T]_. The
moderately disturbed geomagnetic activity of the second half of December is as-
sociated with microseismic activity, whereas the same magnetic activity in mid-
-late November (16-26) is not. This results in significantly higher temperature
in the former period (nearly by 10°C) contrary to the expected seasonal trend.
These findings show that microseisms could probably be used as a check of the
meteorological efficiency of individual geomagnetic storms.
F - 59
There are two exception to the tendency above mentioned. On October 23-26
a strong micro3eismic burst and a medium enhancement of geomagnetic activity we-
re observed, but no effect in Ti. The effect of December 16-17 (a?) is strong
in microseisms, weak in Ti (supports slightly enhanced temperature) and none or
very weak (December 13) in geomagnetic activity. They are both long-periodic mi -
croseisraic bursts (7-8 sec), i.e. their source regions are either Iceland, or
Jan Mayen Is., or the Baltic region, but not the Norwegian regions (Zatopek,
1963). According to meteorological maps, quick passes of well-developed cyclo-
nes across the Icelandic microseismic region occurred on October 23 and October
26. The timing of the passes is consistent with microseismic timing. The same
is true for the Icelandic and Jan Mayen Island regions as regards the December
16-17 event. Rapid decreases of microseismic activity are coincident y/ith the
movement of these cyclones over the Scandinavian part of the continent. Thus, we
find meteorological causes of microseismic bursts in both events. As for the Oc-
tober event, no T\ response is probably due to the T\- station being located far
to the east and to the non-global character of the event as a result of the ob-
served development of geomagnetic activity. A similar situation existed during
the December event. The effect is again probably non-global due to an insuffici-
ent geomagnetic precursor.
According to Bucha (1976), several days after an enhancement of geomagnetic
activity a W-to-E circulation is established over Central Europe due to enhanced
cyclonal activity in the North Atlantic frontal zone. This results in a decrea-
se of the summer temperature and an increase of the winter temperature at Prague
7-12 days after the geomagnetic storm and, if geomagnetic activity continues,
after another 5-7 days. The winter Prague temperature decreases significantly
about 15 days after a decrease of geomagnetic activity (Bucha, 1976). The Prague
temperature (upper curve T2 in Fig. 3) really does not reflect geomagnetic and
microseismic variability in the autumn months of October and November significa-
ntly, as expected. In winter we observe the predicted effects. The deep and well-
-expressed decline of geomagnetic activity in late November, associated with mi-
croseismic calm, is followed by a rapid decrease of Prague temperature 15 days
later, as indicated in Fig. 3. The magnetic activity enhancement of early Decem-
ber is weak and the related microseismic burst only moderate. This results in no
detectable effect in the Prague temperature (it is overlapped by the effect of
the foregoing calm period). The temperature returns to normal (or a little hig-
her) values on December 15, just 7 days after the enhancement of geomagnetic ac-
tivity of December 8-10. However, this temperature is not as high as might be ex-
pected from geomagnetic data, because the associated microseismic burst is of me-
dium importance only. The greatest increase of temperature in the studied period
was observed after December 25, i.e. 7-10 days after another enhancement of geo-
magnetic activity* as indicated in Fig. 3. This enhancement of magnetic activity
is a little smaller than the foregoing one, but is accompanied by a strong micro-
seismic burst and, therefore, by a large increase of Prague temperature. Conse-
quently, microseisms can also serve as a testing tool of geomagnetic storm effi-
ciency in the weather of Central Europe.
The Prague and, generally, Central European meteorological microseisms can
be used for studying meteorological responses to extraterrestrial influences con-
nected with geomagnetic bursts and for estimating the efficiency of individual
magnetic activity enhancements (bursts) in both high-latitude and Central Euro-
pean meteorology. They are useful for short-range (of the order of one week) fo-
recasts of Central European weather. All the results are rather preliminary, be-
cause they are based on an analysis only covering three months, but they appear
F - 60
to be reasonable and they do not contradict the findings of other authors. A
prediction technique, based on geomagnetic and microseismic data, will be deve-
loped in future.
5. CONCLUDING REMARKS
It is worth noting the importance of the 35°N latitude. The general smoothed
pattern of winter microseisms is the same down to about 35°N latitude in Europe
and Japan (Zatopek, 1975). The 35 N latitude is also the approximate equatoward
boundary of the occurrence of the winter anomaly (Wakai et al., 1970) and geo-
magnetic storm effects (Beynon and Williams, 1974 - 37°N) in radio-wave absor-
ption in the lower ionosphere. This points out the importance of the region of
35°N latitude found earlier in global meteorological studies.
The Prague meteorological microseisms have been recorded continuously from
1948 to 1968. Later on the seismograph lost its quality and recording was stop-
ped. When, some time ago, it was found that microseisms could be useful in so-
lar-terrestrial studies, the microseismic data of the nearby (distance about
11.5 km) seismic station of Pruhonice began to be evaluated back to 1968. This
project will be finished completely in the near future. Based on the 1968 data,
the relation between Prague and Pruhonice microseisms was established by Prochaz-
kova (1978) in order to provide a homogeneous series of data since 1948. We are
now beginning to study these new microseismic data (e.g. Fig. 3).
Meteorological microseisms have various advantages and disadvantages. They
are quite inexpensive to obtain as they are a by-product of seismic monitoring
and the only .effort and cost necessary consist in evaluating seismic records from
a microseismic viewpoint. The Prague microseisms provide information about the
North Atlantic frontal zone, which is very important for European weather. On the
other hand, microseisms provide only indirect information, which is "contamina-
ted" by their strong seasonal variation and which may sometimes be difficult to
interprete due to the possible action of several different source regions.
Microseisms in different regions must first be carefully studied to identify
their source regions, which are significantly affected by geological conditions
of microseismic wave propagation. For example, the microseisms recorded on the
Scandinavian Peninsula and Russian Platform have source regions different from
those of Central Europe microseisms (Zatopek, 1961).
In conclusion it can be said that the meteorological microseisms, recorded in-
land, are an inexpensive and valuable additional tool for studying sun-weather
relationships on both the long-period and short-period scale, as well as for im-
proving weather forecasts on a time scale of the order of one week.
REFERENCES
Beynon, W. J. G., and E. R. Williams (1974): Magnetic activity and ionospheric
absorption. J. Atmo3. Terr. Phys., 36:699.
F - 61
Bucha, V, (1976): Variations of the geomagnetic field, the climate and weather.
Studia geop_h. et geod.« 20: 149 ♦
Bucha, V, (1977): Mechanism of solar- terrestrial relations and changes of atmos-
pheric circulation, Studia geoph. et geod.. 21:350.
King, J.W. (1975): Sun-weather relationships. Aeron. Astronautics « 13:10 (also
Solar-Terrestrial Physics and Meteorology: A Working Document, SCOSTEP Se-
cretariat, Washington 1975).
Lastovicka, J. (1974): Relationship between microseisms, geomagnetic activity
and ionospheric absorption of radio waves. Studia geoph. et geod. « 18:307.
Lastovicka, J. (1977): The interplanetary magnetic field sector structure and
meteorological microseisms. Studia geooh. et geod.. 21:168.
La&tovicka, J* (1978): Lower ionosphere, lower atmosphere and IMF sector struc-
ture in winter. Presented on KAPG Symp. "Energy Content and Transfer in
the Atmosphere", Sopron, Hungary (also J. Atmos. Terr. Phys. 41:995).
Mustel, E.R., V. E. Chertoprud, and V.A. Khvedeliani (1977): A comparison of
changes of the surface atmospheric pressure field during periods of high
and low geomagnetic activity. Astron. J* . 54:682 (in Russian).
Prochazkova, D. (1978): Relation between microseisms recorded at seismic stati-
ons Praha and Pruhonice. Studia Geoph. et Geod., 22:362.
Wakai, N., C. Ouchi, and C. Nemoto (1970): Winter anomaly of ionospheric absor-
ption as observed in Loran-A signals. J. Radio' Res. Labs. Japan. 17:185.
Zatopek, A. (1961): Sur la nature et 1 origine des microseismes europeens. Stu-
dia geooh. et geod.. 5:51.
Zatopek, A. (1963) : Uber einige Ergebnisse der statistischen Periodenerfors-
chung von europanischen Mikroseismen. Studia geoph. et geod.. 7«164.
Zatopek, A. (1964): Long-period microseisms generated in eastern part of Atlan-
tic frontal zone. Studia geoph. et geod.. 8:127.
Zatopek, A. (1966): Private communication.
Zatopek, A. (1975): On the long-term microseismic activity and some related re-
sults. Studia geoph. et geod.. 19:14*
Zatopek, A. (1976): On the sources of meteorological microseisms observed in
Central Europe. Acta Univ. Qui. A 43. Phys. 12:21 (also Sec. Rept. IASPEI
Com. Microseisms).
Zatopek, A., and L. Krivsky (1974): On the correlation between meteorological
microseisms and solar activity. Bull. Astr. Inst. Czech.. 25:257.
Zatopek, A., L. Krivsky, and J. Lastovicka (1976): Correlations between solar,
interplanetary, geomagnetic, ionospheric, atmospheric circulation and mi-
croseismic phenomena. J. Interdisciplinary Cycle Res.. 7:9.
62
" ON THE VARIATION OF THE ANNUAL MEAN SEA - LEVEL PRESSURE IN
LATITUDE ZONES OF THE NORTHERN HEMISPHERE "
J. XANTHAKIS, B. TRITAKIS and B. PETROFOULOS
Research Center for Astronomy and Applied Mathematics
Academy of Athens
1**, Anagnostopoulou street, Athens ( 136 ), Greece •
The mean annual sea-level pressure P-P0 within 10°— wide lati-
tude zones of the Northern Hemisphere have been studied in relation
to the 11-year solar cycle. A close correlation between P-PQ and
the sunspot cycle in the Northern latitude zones 50o-60°N,60o-70°
N and 70°-80°N is obvious while no correlation was found in the
zones lower than the 50° parallel of the earth. The extrapolation
of the analytical expression for the mean annual sea-level pressu-
re after 19&0, which is the end of the time-series under conside-
ration, shows an encouraging agreement with the observations of
the few stations which have published more recent data. The lat-
ter conclusion is promising as a means of a rough prediction of
the mean zonal sea-level pressure.
INTRODUCTION
In previous extended papers (Xanthakis 1973*1975) (Xanthakis
et al. 197*0 (Xanthakis and Tritakis 1977) we have made a global
survey of the rainfall as well as a definition of the analytical
expressions of the precipitation, within various latitude zones
10°-wide in relation to the solar activity. In the present paper we
extend our previously described technique to the study of the sea-
level pressure within the same latitude zones of the Northern he-
misphere. Our data source, as in the previous papers, is the
63
" World Weather Records " which contains a large number of sta-
tions with observations available till i960. To maintain the
uniformity of the time-series we did not consider nev stations
after i960. We only used data from the stations that were opera-
tive long before i960, which were collected from microfiches
published by the "World Weather Records ". Thus, an approximate
forecasting of the quantity P-P is more reliable.
1. PREDICTION TECHNIQUE
For each station we calculate the differences :
Pi - Po
where P . are the annual mean sea-level pressure values and F
1 r c
is the minimum of the P.-values during the whole period of obser-
vations at a given station. Next, the average of these departu-
res at the different 10° latitude zones is calculated :
^o = 4-2.( pi - po >
where N is the number of stations located in a particular latitu-
de zone. The correlations obtained between the annual values
of P - P and two solar activity indices ( area index I after
o J a
Xanthakic (1970), and the Zurich relative sunspot numbers R )
where found not to be statistically significant in the follow-
ing latitude zones : 0°-10°N, 10°-20°N, 20°-30°N, 30°-40°N and
i+0°-50° N. These time series display only a long-term fluctua-
tion (trend), which will be referred to as L , and sinusoidal
fluctuations with short periods, between 3 and 7 years, and dif-
ferent amplitudes, which will be called as W. The W oscillations
occur in a successive but irregular manner being sometimes super-
imposed and perhaps mutually complementary.
In the latitude zones confined by the equator and the 50°N
parallel, the corresponding time series of the variable P-P
6*»
can be represented for each 10° latitudinal zone by the analy-
tical relation :
P - P = C + L. + W (1)
o t
where C is the long-term averages of the above variable (P - P ) •
The analytical expression of the L+ term is determined from the
calculation of 11«-year moving averages of the (P - P )• From
conventional Power Spectrum Analysis we have also determined the
short-term W -fluctuations. Their amplitudes and phases have
been graphically inferred from the differences ( P-P ) -C-L. .
o t
Table 1 shows the number of stations used in the analysis as
well as the values of CtL. and W for each latitude zone (from
0* to 50°N) (fig. 3).
Significant correlation coefficients between (P-P ) - L.
c t
and the solar activity indices I and R were found only in
the high latitude zones (northern than 50°N) (see fig.1). As it
can be seen from Table 2, and figure 1, these correlations
changed sign during the period of records. Thus, in the zone
50°-60°N, the correlation was negative during the time interval
1885-1901, positive between 1902-192**, negative between 192^-195.4
and again positive from 1955 onwards. The change in the sign of
these correlations occurred more often in the latitude zone 60°-
70°N while in the zone 70°-80°N the correlation changed sign on-
ly once in the period from 1889 to i960. A similar change in the
sign of the correlation has also been observed in zonal rainfall
departure- (.Xanthakis, 1975)*
Scherhag (1950) Koppcn ( 191*0 and Troup (1962) reported a
similar change in the winter temperatures of Berlin and the
temperature in the tropical zone.
It is noteworthy that although these correlations were not
very strong they v/ere statistically significant at the C,01 le-
vel.
It is also interesting that the change of the correlation
F - 65
TABLE 1
CHARACTERISTIC PARAMETERS OF THE LATITUDE ZONES FROM 0°- 10° to 70°- 80°N
ZONE 0-10 N
0 0
Long. 159,2 W to 151,8 E, Interval : 1890 - 1960
Number of Stations 5 ^ 15, ST.DEV = - 0,06 mb
P - P = 1,95-0,40sin -~- (T-1870) - 0,20sin —~ ( T - 1 886 ) + a sin — -- t
1870-1950 1886-1919 " ^n
1919-1962
1962-1995
where a varies between -0,60 f +0,80 and ¥ = 4 or 6
n n
ZONE 10 - 20 N
0 0
Long. 99,2 W to 123, E, Interval : 1886 - 1960
Number of Stations 9 -V 24, ST. DEV = - 0,06 mb
P - P = 1,95 - 0,55sin -~-( T - 1 864 ) - 0,50sin -~-( T - 1918 ) + 0f70sin-~
° 1918-1958
( T - 1958 ) ± 0,30sin -~(T - 1 908 ) + a sin -|--t
1958-1998 - 1908-1941 R n
♦ 1915-1937
+ 1937-1970
where ap varies between -0,50 -J- 40,60 and^t = 4,5,6 or 7.
0 0
ZONE 20 - 30 N
o o
Long. 157,8 W to 49,1 E , Interval : 1 882 - 1960
Number of Stations 12 7 22, ST.DEV. = - 0,07 mb
P~^~"P = 2,23 + 0,50sin ---- ( T - 1886 ) + 0,40sin -—-{ T - 18^6 ) a sin --- t
° 1886-1904 1866-1938 n
1922-1976
• *
where a varies between -0,70 f -KD,50 and ¥ = 4,5,6 or 8
n n
F - 66
TABLE 1 (continued)
ZONE 30-40 N
0 0
Long. 122,4 W to 149,0 E, Interval : 1883 - 1960
Number of Stations 25 t 44, ST. DEV. = - 0,08 mb
P - P = 2,21 - 0,30sin ----( T - 1860 ) + 0,30sin ----( T - 1949 ) +q sin -~ t
° 1860-1980 'n ^n
where a varies between -0,50 - +0,60 and ¥ = 4 or 8
n n
ZONE 40 - 50 N
0 o
Long. 123,3 W to 132,8 E, Interval : 1882 - 1960
Number of stations 36 i 52, ST. DEV. = - 0,07 mb
2jt , -r „,-,„., \ . 2jt
P - P = 3,71 + 0,45sin -==-( T - 1881 ) +a sin ---- t
o 90 n ¥
n
*
where, a varies between -1,30 V +1 and ¥ = 3,4,6,7, or 8
ZONE 50 - 60 N
0 0
Long. 170,2 W to 158,7 E , Interval : 1885 - 1960
Number of Stations 21 f 50, ST. DEV = t 0,10 mb
P - PQ = Set + L + W, where
S = 3,60 - 0,02 I , ( within the intervals 1885 - 1901, 1925 - 1954)
a a
5a A 2,30 + 0,02 I , ( within the intervals 1902 - 1924, 1955 - )
L^ = 0,10sin -~- ( T - 1865 )+ 0,10 sin -«- ( T - 1 905 )
t 80 "40
- 1905-1945
+• 1945-1985
W = a sin -.Tl — t
n Y
n
F - 67
TABLE 1 (continued)
Where, a varies between -0.50 +0,80 and V - 3 or 6
n ' • n
ZONE 60°-70° N
Lonjr.165,4 W to 177*6 E , Interval : 1889-1960
Number of Stations 11-25, ST.DEV = - 0,06 mb
P - PQ = Sa ♦ Lt«fW, where
Sa = 5,53 - 0,03 Ia ♦ (within the intervals 1889-1902,
192A-1933 19^8-195*0
Sa- 3,70+0,0^ Ia , (within the intervals 1903-1923, 193^-19^7, 1955-1960)
L = 0,25sin ----(T - 1879) - 0,25sin ----( T - 1880)
Z 80 22
W = a sin 1
n Yn
where a varies between -2,20 - +2,00 and ¥ = H or 6
n * ' n
ZONE 70°- 80°N
Long. 156,0 W to 80,^ Ef Interval : 1889 - 1960
Number of Stations : 1-9, ST.DEV. = - 0,06 mb
P - PQ = Sa + Lt + W, where
Sa = 4,49 - 0,03 Ia (within the. Interval 1889-1906)
Sa = 3,5^ + 0,02 Ia (within the interval 1907-1960)
L. = 0,50sin --- (T-l884)-0,50sin --- (T-1912) - 0,50Rin -^-(T-lSSO)
* 80 33 22
1912-1963 1869-1913
1913-1057
1957-2001
W =a nsin — ^-- t
n
where, a varies between -1,00 4*1.20
n T ?
F - 68
10 20 30 40 SO 60
1885-1001
1025-1954
1002-1024
1055- 1080
> zone so-eo N
1680-1002
1024 - 1033
1048-1054
1003-1023
1034-1047
>ZONE6070»N
1880-1006
>ZONE70o-80°N
1007-1060
FIGURE 1| DISPERSION DIAGRAMS OF THE QUANTITY (P - P ) - L
AND I FOR THE LATITUDE ZONES 50°-60°N 60°-70°N
AND 70°-80°N. ASTERIKS REFER TO THE VERY FEW CASES
WHERE THE CORRESPONDING VALUES ARE TAKEN FROM 1:2:
1 SMOOTHING.
F - 69
'TABLE 2
CORRELATION COEFFICIENTS BETWEEN (P - P )-L^
o t
AND THE INDICES OF THE SOLAR ACTIVITY I , R
a m
LONE
(P-Po)-Iv I
<p-Po>-LfRr
TIME INTERVAL
^0°-f>C°
+0,71
-0,48 1885 - 1901, 1925 - 195V
+0,49 1902 - 1924, 1955 - 1960
6o°-70°
+0,46
-0,51
+0,49
-0,60
1903
1955
1889
19^8
1923, T934
1960
1902, 1924
1954
- 1947
- 1933
70°-8o°
-0,70
+0,50
-0,54
+0,36
1889 - 1906
1907 - 1960
TABLE
LONG - TERM AND SHORT - TERM FLUCTUATIONS OF P - P IN THE 10°
o
WIDTH LATITUDE ZONES OF THE NORTHERN HEMISPHERE
ZONE!
FLUCTUATIONS
0°-10°
4
6
22
10°-20°
4
5
6
7
22
20°-30°
4
5
6
30° -40°
4
8
40°-50°
50°-60°
3
#
3
4*
6
6*
7
60°-70°
4
6*
22
70°-80°
4
6
8
22
36
40
40
40
33
80
80
80
80
80
80
90
statistically significant fluctuation at a confidence level lower
than 0,05.
70
sign between (P-P ) -L. and I occurs near the extrema of the
° ota
solar cycle.
In the high-latitude zones the time series of the P-P varia-
° o
ble can be approximated by the analytical relation
P - PQ = Sa + Lt + W (2)
where Sn represents the repression line between ( P - P ) - L.
•* * ^ o t
and the areas index Ia . The analytical expressions for Sa , L
and W are given in Table 1 (zones 50° to 8o° N) . Table 3 below
shows the "periods" of the oscillations L and W for all latitude
zones. It is interesting that the long-term fluctuations diplay "
"periodicities " of 22 and 80-90 years and sometimes multiples or
submultiples of them. The fluctuations of k0 and 80-90 years
can hot be further discussed with respect to any "cyclic " behaviour
because of the shortness of the record (less than 80 years).
This is not the case, however , with regard to the 22 year
fluctuations which appear twice or three times sometimes changing
their " phase " and thus displaying a " cyclic " behaviour.
The results from the calculations through the relations (1)
and (2) are presented graphically in Figs, 2 and 3«
CONCLUSIONS
The variation in the zonal averages of annual mean sea-level
pressures have in general small amplitudes of the order of 2 to
3 mbs. These fluctuations were not correlated with the solar
activity indices Ia and R in the zones between the equator and
the 50°N parallel. In the high latitude zones, however, there
was an appreciable correlation, statistically significant at the
99# level, which changes sign at various times.
The fluctuations of the variable P-P can be represented
o r
with high accuracy through the relations (1) and (2) with corre-
sponding standard deviations cf the order of - 0.05 to - 0.08 mbs.
71
1880
I i
1890
i I i
1900 10 20
' i I i i i i I i i i i I
30
i i I i
40
i i i i i i i
1950
i I i
60
i I i
70
i I
80
i i i I
A
E
2.0-
1.0-
3.0-
2.0-
O 1,0
CL
l
Q.
^
30°-40° fSy . fj^MX-—^
5,0- 40°-50°
4.0-
3.0-
-3.0
-2.0
-1.0
-3.0
-2,0
-1.0
FIGURE 2 : ANNUAL VARIATION OF THE QUANTITY C+Lt (CONTI-
NUOUS LINE) AND THE CALCULATED VALUES OF P^PQ FROM
THE RELATION (1) (DASHED LINE). THE CIRCLES REPRE-
SENT THE OBSERVED VALUES OF P^PQWHILE THE CROSSES
CORRESPOND TO THE DATA OF A FEW STATIONS WE USE
FOR CONFIRMATION OF THE PREDICTION.
72
1880 18*0 1900
1950 60 70 80
i i i |
1880 1890
Years
FIGURE 3 : ANNUAL VARIATION OF THE QUANTITY Sa+Lt (CONTINUOUS
LINE )AND THE CALCULATED .VALUES OF P~^P0 FROM THE
RELATION (2) (DASHED LINE).
THE VERTICAL CONTINUOUS LINES CORRESPOND TO THE
MAXIMUM OF THE SOLAR ACTIVITY WHILE THE BROKEN ONES
TO THE MINIMUM OF IT.
THE CIRCLES REPRESENT THE OBSERVED VALUES OF P^P
c
WHILE THE CROSSES CORRESPOND TO THE DATA OF A
FEW STATIONS WE USE FOR CONFIRMATION OF THE PREDI-
CTION*
F - 73
§-
ft-
6-
ft-
ft-
6
r\l-
ft-
i-
L
L
o
3)
-ft
_6
-ft
_t>
CM
-o
_6
<7>
-I
_&
-ft
-ft
-i
.ft
-5
_ft
LU
a
i — i
in
^
□
(_j
cr
UJ
O
^
3
in
2
a
i— i
i—
•
<t
i—
0_
in
4-
UJ
o
a:
I—
LJ
M
L_
i— i
a
LO
2
LJ
a
>
i— i
i— i
l—
H-
Z)
<=r
GD
_l
i— i
LU
cr
cr
I—
LO
cr
i— i
1—1
O
UJ
n:
_l
i—
<:
^
Q
i—i
2
□
<C
ID
1—
2
i—i
a
LT
i—i
2
l—
a
<c
_i
en
LU
cr
ZD
LD
F - 7A
1 1 1 — 1 1
<fi a o 00°
1 1
ZONE O'-IO'N
o & 8° 3>o o » «f.g '»08°o° *?e&' °^oo<> s ""^
ZONE 1O'-20'N
0 »0<SC% ^>"o * o»° " O0^foO/ "^ o^ooS 0*°°
| 1mb
ZONE 2Cf- 30- N
° * o o° °0°° ° o°° o oo o „° 8,3,, V " CPO
ZONE 30«-40'N
o°o0 %V«pO ° " o» o° «» o ^ 0^ o
ZONE 40«-50'N
1 1 1 1 1
' '
' i
la
FIGURE .5 : DISPERSION DIAGRAMS CF THE QUANTITY (P-PQ)-Lt
I FOR THE 10° WIDE LATITUDE ZONES 0°- 50° N.
a
AND
In view of the relative shortness of the record, no cyclic beha-
viour can be attributed at present to the long-term fluctuations
component L . Finally, the encouraging agreement of the extrapola-
ted analytical expression of P - P with the data of a few sta-
tions which continue their observations after i960 in the latitude
zones 0°-10cN, 10°-2C°, 60°-70°N and ?0°-80°N, indicates a simple
way of prediction for the mean zonal sea-level pressure.
The extrapolated analytical expression of F-P after i960 did
not include short-term fluctuations W because of the difficulty
to define their position and amplitude.
75
REFEHNCES
hoppen, W. ( 191^+) : Lufttemperaturen, Sonnenflecke und Vulkanau-
sbruche, Met. Zeit., 3*1 « 305-28 .Braunschweig.
Scherbag, R. C 1950) : Bestehen Zusamraenhange Zwischen der elfja-
hrigen Sonnenfleckenperiode und der allgeraeinen Zirkulation?
Deutsche Hydr. Zeit., 3, 108-11. Hamburg.
Troup, A. J. (1962): A secular change in th£ relation between the
Sunspot Cycle On temperature in the tropics, Geoph?sica
pura e applicata, j>1, l8'f-98. Milan.
Xanthakis, J. (1970) : On a relation between the indices of so-
lar activity in the photosphere and the corona, sol.phys
10 : 168. ~
Xanthakis, J. (1973) s Solar activity and Precipitation. Proc. of
st ~~ ~~ ~~
the 1 " European Astronomical Meeting, Athens, September
^tft, 1972, vol. 1.
Xanthakis, J,, C.Poulakos, and Bf Tritakis ( 197*0 : Solar activity
and precipitation within the zones of latitude O'-'fO'N,
Praktika of the Academy of Athens kS : 187
Xanthakis, J. (1975) ' Solar activity and a global survey of
the precipitation. Papers of theo Academy of Athens No. 37
Xanthakis, J., and B. Tritakis (1977) '• Analytical expression of
the mean annual variation of the precipitation within va-
rious latitude zones of the earth. J. interdisc. cycle Res.
8 : 226
F - 76
THE 13.6-DAY OSCILLATION IN THE STRATOSPHERE
A. Ebel
Institute for Geophysics and Meteorology, University of Cologne
D-5000 Cologne k\ , F.R.G.
A 13- 6-d oscillation of zonal ly averaged height differences of
the 10-mb surface, which is significantly correlated with solar ac-
tivity fluctuations, is analyzed with respect to its statistical
properties. The oscillation can be interpreted as a zonal wind
perturbation in the northern hemisphere. The gain obtained by
means of spectral analysis for the "10-mb surface" system appears
to be relatively fixed in time. The latitudinal dependence of
gain and phase resembles that of basic modes with zonal wave num-
ber zero for oscillating layers on a rotating sphere. The statis-
tical model of a linear system with one input and output can be used
to derive a "prediction" equation for a mean 13. 6-d oscillation.
The implications of the model concerning the temporal behavior
of the stratospheric system are discussed showing that the 1 3 - 6-d
oscillation is only one example — and a relatively simple one — of
possible solar activity effects at 10 mb in a broader range of
oscillation frequencies.
1. INTRODUCTION
Comparing daily values of the 10.7-cm flux of the solar radiation and
zonal indices of the 10-mb circulation, a 1 3 - 6-d oscillation of the zonal mean
wind responding to solar activity changes has been found at the height of the
10-mb surface in the northern hemisphere between 10°N and 80°N (Ebel and Batz,
1977). The oscillation has been extracted from the 10-mb data applying the
methods of spectral analysis of time series (Jenkins and Watts, 1968). In-
herent in this form of bivariate time series analysis is the assumption of a
linear system (the 10-mb surface) having one input (solar activity "process-
es") and one output (zonal index changes) determined by the response function
of the system. Using this simple model of solar activity/stratosphere (10 mb)
interaction it is easy to arrive at a prediction of the 13. 6-d oscillation
provided the response of the system and the input function are known or can
be predicted for this oscillation period, as discussed in Section 3.
The phenomenon studied here and briefly described in the next section is
certainly of minor importance compared to other meteorological effects in the
stratosphere. In terms of wind it is a perturbation of less than 0.6 m/s
F - 77
(Figure 1). Nevertheless, there are good reasons to study even such minor
effects as far as the understanding of the physics of the stratospheric sys-
tem and the application of statistical techniques to the analysis of this and
similar systems are concerned:
1. Little knowledge and contradicting findings (e.g., Gerety et al.,
1977; King, 1975; Olson et al., 1975; and Wilcox et al., 1976) and ideas exist
with respect to the problem of how deep and how efficient solar activity ef-
fects, which are well established at least down to the mesopause, can pene-
trate to lower atmospheric layers.
2. The 13-6 - d oscillation resembles some features found theoretically
for oscillating layers on a rotating sphere (Longuet-Higgins, 1968); this
gives some support to the assumption that statistics have helped to unravel
some of the real behavior of the 10-mb surface.
3. There is good evidence that other oscillations with periods differ-
ent from 13-6 d (which is approximately half the rotation period of the sun)
are also correlated with solar activity oscillations; this may help to ex-
plore the variability of the stratospheric system and thus improve cl ima to-
logical studies.
k. The 13-6-d oscillation can be described with simple meteorological
(physical) quantities and has a simple morphology. Therefore, it Appears
to be especially suited for the study of some principal problems concerned
with the statistical methods used for investigating solar activi ty /weather
relat ionsh ips.
The purpose of this paper is therefore not so much the outline of a sim-
ple "prediction" technique for a single line in a broad spectrum of strato-
spheric oscillations as it is an attempt to clarify the assumptions necessary
for progression from the (statistical) diagnosis of a sun-weather phenomenon
to its prediction. This attempt is made in Section k where the stability of
the "10-mb surface" system is analyzed. In terms of spectral analysis it is
the frequency response function which is discussed. The present dtudy is re-
stricted to this topic, but it should be noted that the determination of the
second component required for a prediction, namely, the input function "solar
activity" might lead to similar problems like the evaluation of the response
function.
20
E
c
q
a
.0
c
Jr. -20
-40
-60
^^^ — "®s
\
period 13.6 d
linewidth 0.007 d"
\
20
40
latitude
60
80 °N
Figure 1. Perturbation
of the mean zonal compo-
nent of geostrophic wind
correlated with solar
activity oscillations at
frequency 1/(13. 6d).
Encircled crosses; co-
herency estimate exceeds
95% confidence limit.
Width of spectral line=
0.007 d"1.
F - 78
2. PHENOMENOLOGY OF THE 13-6-d OSCILLATION
For a detailed description of the 13-6-d oscillation of 10-mb indices
and a complete discussion of its statistical significance, the reader is re-
ferred to Ebel and Batz (1977). Only a brief summary of the applied data and
final results is given here.
The zonal 10-mb indices (l) are defined as the zonal ly averaged height
differences of the 10-mb surface for two latitude circles <h and <J>2 separated
by 20° (cf>2 - <h - 20°):
1 n
I (*l, 4>2) = 7T I [h.Oh) " h.(<j>2)] (1)
n i = l '
where hj is the geopotential height in gpm at n (normally 36) gridpoints on
the latitude circles at 10°, 20°, ... 80°N. These data have been provided by
the Meteorological Institute of the Free University of Berlin for the period
November 196^-October 1971. The zonal 10-mb index can be interpreted as the
zonal ly averaged geostrophic wind v (in m/s) using the relationship
v = 0.03 l/sin(<h + 10°) (2)
For monitoring the solar activity, daily values of the 10.7-cm flux of the
solar radiation (briefly S10.7, in units of 10"22W m"2 Hz-1) have been chosen,
Correlating the total time series of the 10-mb indices and of S10.7 a clearly
significant coherence estimate was obtained at or near an oscillation period
of 13-6 d, corresponding to half the rotation period of the sun. This is true
for all latitude belts except for the index for *t0°N-60°N. Coherence estim
mates, the gain for the 10-mb index, and its confidence limits are found in
Table 1, part A, which also contains the phase estimates for the oscillation.
Evidently, the oscillations at 10-mb are nearly in phase with the solar ac-
tivity oscillations at latitudes below 50°N, and they are out of phase above
50°N (with a lag of roughly one day). Using the autospectral estimate for
the indices at frequency f, C||(f), the coherence squared, K2(f), and an es-
timate of the bandwidth of the correlated signal, Af, one arrives at an ap-
proximate amplitude I ' (f) of the oscillation of I given by
l'(f) = [K2(f)C,,(f)Af]35 (3)
Inserting the result into equation (2), an estimate is obtained for the ampli-
tude of the quasiperiodic zonal wind perturbation at frequency f in a given
latitude belt. The result for f = 1/(13.6 d) is shown in Figure 1, where in-
phase oscillations are assigned to positive perturbations.
3. FREQUENCY RESPONSE
In principle, equation (3) is equivalent to the relationship
c},(f) = G2(f)Css(f) ik)
F - 79
Table 1. Estimates of gain, squared coherency, and phase.
[Gain in gpm/(l0"22W m"2H2_1), phase in degrees (positive if S10.7 leads).
Degrees of freedom 33 (part a) and 29 (parts B and C) . Bandwidth 0.0067 d"1
(A) and 0.0133 d" (B and C) . Tukey window used. 95% confidence limit of
coherency squared for prior selection 0.12. Solar activity spectral
estimate Ccs in ( 10"22W m"2Hz_1 ) 2d. 95% confidence interval is
(0.64, 1.7) x Css.]
Latitude (°N) : 10-30 20-40 30-50 40-60 50-70 60-80
A.
Period 11/64-10/71,
sol.
act. spectral estimate 1
.6xl05,
f = 0.0738 d"1.
Gain
0.039 0.076 0.081
0.044
0.24 0.54
95% conf . interval ,
gain
±0.039 ±0.055 ±0.072
--
±0.20 ±0.38
Squared coherency
0.15 0.27 0.25
0.06
0.22 0.22
Phase
36 2 27
88
201 235
B.
Period 12/64-11/67,
sol .
act. spectral estimate 3
.4xl0\
f = 0.0750 d"1.
Gain
0.048 0.023 0.093
0.16
0.13 0.63
95% conf. interval ,
gain
—
—
—
Squared coherency
0.07 0.02 0.06
0.11
0.02 0.08
Phase
106 161 179
125
-83 -53
C.
Period 10/68-12/70,
sol .
act. spectral estimate 1
.9xl05,
f = 0.0750 d"1.
Gain
0.054 0.071 0.094
0.046
0.24 0.43
95% conf. interval ,
gain
±0.028 ±0.054 ±0.087
--
±0.21 ±0.43
Squared coherency
0.46 0.28 0.23
0.06
0.22 0.17
Phase
-8 -9 16
84
195 209
where G(f) is the gain function of the "10-mb+surface" system, Css(f) the
autospectrum of solar activity (S10.7), and C| | (f) a prediction of the output
amplitude (10-mb index) which is only due to the input S 1 0 . 7 • Since
l,2(f) = c|.(f)Af, the perturbation of the zonal index (equation (3)) or of
the zonal mean geostrophic wind (equation (2)) with a given bandwidth can be
derived with the aid of equation (4). The phase estimate F(f) (>0, if the os-
cillation of S10.7 leads that of the 10-mb index) completes the frequency re-
sponse function
H(f) = G(f) exp[iF(f)] (5)
The problem with the application of the "prediction equation" (4) for
C 1 1 is that the gain (and phase) estimates and Css have to be known. From
now on we will concentrate on the first half of the problem, namely on the
investigation of the frequency response characteristics of the 10-mb system
around the oscillation period 13.6 d. The main assumption made for practical
reasons for the derivation of the frequency response function concerns the
stationarity of the stratospheric system at least for the time interval for
which data have been available. If the system does not change in the future,
H(f) should remain constant and the perturbation of the 10-mb index could be
predicted from the input "solar activity (S 10. 7) "• Besides, the hypothesis
of a fixed system is implicitly inherent in most statistical studies of
F - 80
atmospheric systems. No wonder that it causes so much trouble, especially in
investigating solar activity-weather relationships.
Looking at the gain and phase estimates for the 10-mb index in Table 1,
it seems that we are correct in concerning the 10-mb system around the oscil-
lation period 13.6 d (though there is no guarantee for future stationar i ty) .
The data set has been split into two samples, one with low solar activity
(part B) , the other with higher solar activity (C) . The gain exhibits nearly
the same dependence as for the total period of observation (Table 1 , A) in
both cases, though it should be noted that the data for low solar activity do
not result in coherency estimates significant at the 95% confidence limit.
Yet it is evident that for weak input signals (low solar activity) difficul-
ties in arriving at good estimates of the frequency response from the noisy
10-mb system have to be expected. The 95% confidence limits of the gain,
which can be taken as a measure of the quality for a predicted response, al-
ways exceed the gain estimate in Table 1, part B. There is one indication
in the gain estimate that the frequency response at period 13.6 d may change
with time at certain latitudes. The *tO°N-60°N belt shows an unexpectedly
high value of the gain for low solar activity, which is approximately four
times that for the period of high solar activity or for the total period. The
coherency estimate exceeds the 90% confidence limit, whereas it is near zero in
the other cases. It seems appropriate to study the temporal behavior of the 10-
mb system in somewhat greater detail.
Before doing this it should be pointed out that the splitting of the
data set into two separated periods made it necessary to increase the band-
width of spectral computations to get the same degrees of freedom as for the
total period (Table 1, headnote) . Tests carried out by window broadening
resulted in a decrease of the coherency peak showing that the solar activity
effect on the zonal 10-mb indices is narrow banded.
10-mb SURFACE" SYSTEM
The long-term variability of the stratosphere, which possibly also de-
pends on solar activity (Naujokat, 1978) may affect the frequency response of
the "10-mb surface" system — as given by the zonal indices, equation (1) — to
solar activity oscillations. During the period 11/64-10/71, the system ap-
peared to be relatively fixed near the oscillation period 13.6 d, i.e., half
the rotation period of the sun. Yet there are other oscillation periods
where strong correlations between the zonal indices and the solar activity
can be found during shorter time intervals, e.g., individual summer and winter
periods (Figure 2). They can be highly significant in the framework of
statistical methods applied, but they disappear when longer time intervals
are treated. For instance, a coherent 27-d oscillation of the zonal indices
might be expected regarding the very strong power in the S10.7 spectrum due
to solar rotation. Good correlation near the rotation period may occasion-
ally appear during some time at some latitude. Yet it is completely sup-
pressed in longer time series. The autospectra of the zonal indices may even
show a strong minimum near the period 27 d. An example is shown in Figure 3-
The spurious appearance of large significant values in the coherency
spectra derived from short time series of the zonal 10-mb index and S10.7
F - 81
SUMMER
20 - U) °N
WINTER
1965 67 69 71 65*6 67/68 68/69
60 - 80 °N
SUMMER
WINTER
Figure 2. Coherency estimates (K)
for 10.7-cm fluxes of solar radia-
tion and zonal 10-mb indices of the
latitude belts 20-40°N and 60-80°N.
Winter period: October-April.
SUmmer period: April-October.
Degrees of freedom of spectral
estimates: 9.
Bandwidth: 0.0222 d"1 .
Hatched areas: K exceeds 35% con-
fidence limit for prior selection.
Dark areas: 35% confidence limit for
posterior selection exceeded.
Broken line at period 13.6 d.
1965 67 69 71
66/67 67/69 69/70
Figure 3. Autospectra of the zonal
10-mb index for *»0-60°N.
Period of low solar activity:
12/64-11/67.
Period of higher solar activity:
1/68-12/70.
f0 = solar rotation frequency ,=
1/27.2 d.
0.05 010 015
frequency j 6A
020
F - 02
points to the problem of stationarity or stability of the stratospheric sys-
tem. One may distinguish three main causes for spurious significant results:
1. The applied statistical methods are not in agreement with the re-
quirements of the physical system (nonstat ionar i ty , nonl ineari ty , etc.); in
the case of the 13. 6-d oscillation this has to be checked carefully with
future observations.
2. The system may have more than one input leading to output signals,
masking or pretending the expected output; in the case of the stratosphere
one has to expect coupling with the troposphere — a problem still to be in-
vestigated by multivariate spectral analysis for the 1 3 • 6-d oscillation.
3. The system may have discrete and temporarily fixed states and the
transition between these states might itself be a stochastic process. This
point certainly involves the most serious complication in diagnosing and pre-
dicting a physical effect only on the basis of statistical methods in any at-
mospheric system or subsystem such as the 10-mb surface.
To illustrate this problem the coherency between the 10.7-cm flux and
the zonal 10-mb index is compared in Figure 2 for periods larger than six
days as obtained for individual summer and winter periods in two latitude
belts. The coherency exceeds the 95%-conf idence limit for prior selection
in the hatched fields and the limit for posterior selection in the dark
fields on Figure 2. These fields represent roughly 30 percent and 10 percent,
respectively, of the total area. It seems difficult to explain this result
just by inappropriate application of statistical methods. Rather, it ap-
pears that sporadic solar activity effects may show up at the 10-mb surface
in a wide range of frequencies. With a few exceptions they disappear when
longer time series are used. This can easily be explained by limited and
irregular periods of efficiency of the solar activity input and by temporal
changes of the phase relationship between input and output siganls. These
are typical features of stochastic processes.
Further indications of the temporal variability of the stratospheric
system in a broad frequency range (shown for f < 0.15 d-1 in Figure 3) are
contained in the autospectral estimates of the zonal indices (or mean zonal
geostrophic wind) for it0°N-60°N at 10 mb. The variance of the system in-
creases during the period with low solar activity (12/64-11/67, continuous
line). Apparently this occurs systematically concerning the spectral ranges
between the solar rotation frequency and its higher harmonics. The reason
for this is not yet understood.
5. CONCLUSIONS
The discussion in the last section shows that a comprehensive explora-
tion of the relationship between solar activity and stratospheric weather and
climate still requires the solution of numerous problems with respect to the
statistics to be applied. The special case of the 1 3 - 6-d oscillation seems
to indicate that, at least in some limited frequency interval s, certain frac-
tions of the variance of stratospheric quantities can be determined with
simple statistical techniques (spectral analysis) using solar activity
parameters. "Prediction" in this case can only mean the estimate of an
average signal or oscillation over longer periods and thus — for the present —
83
concerns the climate rather than the weather of the stratosphere. The veri-
fication of the findings for the 13- 6-d oscillation in the sense of a pre-
diction method requires 10-mb data at least up to the year 1978, which is not
yet avai lable.
The causes of the relationship between solar activity and the mean zonal
wind at 10 mb near the oscillation period 13.6 d still must be explored.
Speculations about the mechanisms (the role of ozone, connection with the
full rotation period of the sun) are beyond the scope of this paper. They
can be found in the paper of Ebel and Batz (1977).
Acknow 1 edgemen t . The 10-mb data have been provided by the Meteorological
Institute of the Free University, Berlin. Valuable help by Professors K.
Labitzke, G. Naujokat, and K. Petzold, Berlin, is gratefully acknowledged.
Parts of this paper refer to a study supported by the Deutsche Forschungsge-
meinschaft under Grant Eb 56/2.
REFERENCES
Ebel, A., and W. Batz (1977): Response of stratospheric circulation at 10 mb
to solar activity oscillations resulting from the sun's rotation.
Tellus, 29:41 .
Gerety, E. J., J. M. Wallace, add Ch. S. Zerefos (1977): Sunspots, geomag-
netic indices and the weather: A cross-spectral analysis between sun-
spots, geomagnetic activity and global weather data. J. Atmos. Sci . ,
3^:678.
Jenkins, G. M. , and D. G. Watts (1968): Spectral Analysis and Its Applica-
tions. San Francisco: Hoi den Day.
King, J. W. (1975): Sun-weather relationships. Aeronaut- Astronaut., 13:10.
Longuet-Higgins, M. S. (1968): The eigenfunctions of Laplace's tidal equa-
tions over a sphere. Philos. Transact. Roy. Soc. London, A, 262:511.
Naujokat, B. (1978): Long-term variations in the stratosphere of the
northern hemisphere during the last two sunspot cycles. Paper pre-
sented at International Symposium on Solar-Terrestrial Physics,
Innsbruck, Austria, No. TA 8.6.
Olson, R. H., W. 0. Roberts, and C. S. Zerefos (1975): Short term relation-
ships between solar flares, geomagnetic storms, and tropospheric
vorticity. Nature, 257:113.
Wilcox, J. M., L. Svalgaard, and P. H. Scherrer (1976): On the reality of a
sun-weather effect. J. Atmos. Sci., 33:1113.
8k
A CONSIDERATION OF THE POSSIBLE USE FOR WEATHER
FORECASTING OF A PARTICULAR SUN-WEATHER RELATION
R. Gareth Williams and Michael J. Rycroft
Physics Department,
The University,
Southampton, England.
All sun-weather effects being discussed at present are based on
statistical correlations and not on acceptable physical models.
Therefore, it is appropriate to ask whether or not it is possible
to improve meteorological forecasts by using these relations
before we have a thorough understanding of the physics involved.
A particular sun-weather relationship, involving the vorticity area
index (VAI) and the solar sector boundaries (SSB), (Wilcox et al.,
197^» 1976) is examined in order to consider this question for
routine, daily weather forecasting. Wilcox et al. (1975) reported
on the seasonal variations of the effect. Evidence is presented
here showing that the effect is also inconsistent from year to year.
The results of a study of the energetics of the VAI - SSB effect
are also presented. It is concluded that we are, as yet, some way
from using this particular sun -weather relationship as a predictive
tool. It is suggested that the most productive way of moving
towards this goal is to perform new statistical studies specific-
ally designed to obtain a one-to-one sun-weather relationship and
also to provide a detailed, overall picture of the meteorological
effects. Such a relationship could probably be used as a predict-
ive tool and would strongly focus the search for a physical
mechanism.
1 . INTRODUCTION
The "academic" aim of sun-weather relations is to improve our under-
standing of the complex interaction between solar activity, its effects on
the interplanetary medium and changes in the terrestrial magnetosphere,
ionosphere and atmosphere. The "economic" aim is to improve weather fore-
casting. Current understanding of what physical processes might be
responsible for causing a sun-weather effect is somewhat limited. Indeed
the difficulty experienced in finding such processes is one of the mainstays
of arguments claiming that all sun-weather relations must be purely statisti-
cal flukes. Such arguments may or may not prove to be valid, but for the
purposes of this paper it is assumed that physical links between transient
solar phenomena and the troposphere do exist and are of a significant
amplitude. Therefore, we must consider whether the "economic" goal can be
F - 85
fulfilled without first achieving the "academic" one.
There seem to be two major problems to be surmounted before the
"economic" aim can be attained. Firstly, it is necessary to have a one-to-'
one sun-weather effect, i.e. given a particular solar event, a particular
tropospheric response must always be observed to occur. Such a relationship
could also involve any dependence on ambient meteorological conditions and
must allow for variations in the magnitude of the response caused, for example
by variations of the amplitude of the solar impulse. Once an equation of
this type has been found, a detailed description of the response of all the
relevant tropospheric parameters must be obtained. It is not sufficient to
know how the VAI responds; other, more conventional and physical parameters
must be considered.
These two problems are discussed for the particular relationship between
the VAI and the SSB.
2. ONE-TO-ONE RELATIONSHIP
Wilcox et al. (197^> 1976) have reported a significant statistical
correlation between the VAI and the passage of the earth through the SSB.
The correlation was obtained using a superposed epoch analysis and data
covering the years 1963-73 inclusive. The solid lines in Fig. 1a & b
(Williams and Gerety, 1978) are reconstructions of the results of Wilcox et
al. (197^» 1976) and characteristically show approximately a 10^ decrease in
the VAI a day or so after the passage of the SSB.
Wilcox et al. (1975) have also reported on the seasonal variations in the
magnitude of the results. They show that the effect only appears in the
months November through March. Thus it is clear that not all SSB cause
the VAI to decrease. Nor is it sufficient to say that all the SSB occuring
in winter cause an effect. The definition of winter may be lengthened or
shortened by a week or two without seriously effecting the results. There-
fore, we cannot claim as yet to have a one-to-one relationship.
Arguments along these lines become much more forceful when we further
consider the results of Williams and Gerety (1978) as shown in Fig. 1a & b.
As mentioned above, the solid lines are essentially reproductions of the
results of Wilcox et al. (197^, 1976). (For further details of the analysis
techniques used, see Williams and Gerety (1978)). The dashed lines are the
results of analysing new data covering January 197^ through March 1977* The
results shown are for the months November through March. At 500 mb no effect
at all is discernible, and at 300 mb the amplitude of the signal is at best
seriously reduced.
This lack of response is not attributable to the solar minimum of 1976.
Fig. 2 shows the result of analysing in identical fashion the 500 mb data
for the similar >J year period 1 963-66 which covered the previous solar
minimum. Nor is it attributable to variations in the distribution of key-
dates: since a superposed epoch analysis is essentially a cross-correlation
F - 86
CM
IT)
o
54
52
£50
i
£48
46
500 mb
— 1963-73, N = I20
-1974-77, N = 49
_ Nov 1st— Mar 31st
J i L
l
40 —
CM
e
38 £
<
36 >
Is-
Is-
i
a>
34
32
-6-4-2 0 2 4
DAYS FROM SECTOR
BOUNDARY CROSSING
FIG. 1a: Results of Superposed Epoch Analysis of 500 mb VAI using
SSB as keydates (from Williams and Gerety, 1978)
its result may depend on periodicities in either the keydates or the data
being superposed. (Williams, 1978b) However Fig. 3 indicates that there
are no marked differences in the properties of the keydates.
Since we are assuming that sun-weather effects do exist, this surprising
result strongly suggests that many of the keydates used by Wilcox et al.
(197^» 1976) may not have caused a tropospheric response. This implies that
the 10% amplitude has been damped by some null results and that the true
response of the VAI is even more marked. Thus, not only are we missing a
one-to-one relationship, as yet, but also we consequently cannot be certain
of the amplitude of the effect.
This one-to-one relationship, if it is found, will almost certainly not
be simple. It is, perhaps, interesting to note that the typical winter
values of the VAI were much lower during 1 97^—77 than from 1963-73 (see Fig.1 )
Also, the VAI is typically lower in summer than in winter. These two facts
suggest that the explanation of both seasonal and inter-annual variations
may lie in a dependence of the VAI response on the ambient meteorological
conditions. (This possibility is currently under examination)
F - 87
CM
E
O
ro
en
300 mb
1964-73 N=II0
1974-77 N=49
108
106
104-
-6
Nov 1st— Mar 31st
J i L
FIG. 1b:
-4-2024
DAYS FROM SECTOR
BOUNDARY CROSSING
Results of Superposed Epoch Analysis of 300 mb VAI
using SSB as keydates (from Williams and Gerety, (1978)
90
One final point deserves comment in this section. We have asserted
that a one-to-one relationship is required before a predictive procedure
can be established. On the other hand, Larsen and Kelley (1977) have shown
that the ability of the Limited Fine Mesh prognostic model (Ramage 197&) to
predict the VAI correctly, in its 12 hr. and 2h hr. weather forecasts,
deteriorates after the passage of an SSB. This result was arrived at using
the superposed epoch method for h7 keydates occuring during October through
March 1972-7^ and January 1975* This suggests that the statistical averages
currently available to us may be used for predictive purposes. However,
part of the data used overlaps with the period analysed by Williams and
Gerety (1978). This not only implies that the result would have been more
striking if these data had been omitted but also that predictions made
during 197*+ said 1975 would have been on the average, worsened by the inclus-
ion of the VAI - SSB effect. Thus, we feel justified in making our assertion
of the necessity of a one-to-one relationship.
F - 88
48
500 mb
Nov 1st — Mar 31st
1
1
1
1
1
-6-4-2 0 2 4
DAYS FROM SECTOR
BOUNDARY CROSSING
FIG. 2: Result of Superposed Epoch Analysis of 500 mb VAI using
SSB as keydates for Solar 'Quiet' years 1 963-66
O
h-
O
UJ
(/)
o
o
12
10
8
6
4
2
0
J_L
□ 1964-73
1974-77
8 S Js
i h n
FIG. 3:
2 4 6 8 10 12 14 I6 18 20 22 24
WIDTH OF SECTORS IN DAYS
Histogram of sector widths (from Williams and Gerety,
1978)
89
3.
OTHER METEOROLOGICAL PARAMETERS
Once a one-to-one relationship is established, an overall under standing
of the response of the troposphere is required. The VAI is not a convent-
ional meteorological parameter and is not included in prognostic models.
The major purpose of its definition seems to have been the establishment of
a particular sun-weather effect.
Fig. k illustrates the results of one study aimed at understanding the
VAI - SSB effect in terms of more conventional parameters. In this case,
the parameters studied are the four components of the Lorenz energy cycle.
FIG. k'.
1 1.30 1-
Winter
500 mb
-6-4-2 0 2 4 6
DAYS FROM SECTOR BOUNDARY CROSSING
Results of Superposed Epoch Analysis of Lorenz Energy
parameters using SSB as keydates (from Williams 1978a)
90
These four parameters, viz. the eddy and mean zonal, kinetic (KE, KZ) and
available potential (AE,AZ) energies (Dutton and Johnson, 1967) plus the
rates of conversion between them, and their generation and dissipation,
provide an overall description of the flow of energy through the atmosphere.
Moreover, this formulation has the advantage that we may expect KE to be
related to the VAI since each is, to some extent, a measure of large scale
eddies in the atmosphere.
The results of performing a superposed epoch analysis on the four para-
meters at 500 mb are shown in Fig. k (Williams, 1978a) The keydates used are
the SSB. The parameters were calculated using the National Meteorological
Center dataset stored at the National Center for Atmospheric Research,
Boulder, Colorado, U.S.A. The parameters are averages for the Northern
Hemisphere, north of 20°N. and were calculated daily, from June 19&3 to
June 1976, using a computer program due to McGuirk and Reiter (1976).
The error bars were calculated in identical fashion to that of Hines and
Halevy (1977)* Winter is defined as November 1st through March 31st.
The parameters AZ, AE and KZ do not show much response to the SSB.
However, KE is interesting in that in winter it shows a variation similar to
that of the VAI. The result is not as statistically significant as the VAI -
SSB effect and the minimum occurs a day later; on the other hand, its annual
and seasonal variation and its altitude dependence are similar to that of the
VAI - SSB effect (see Williams, 1978a, for a fuller discussion).
In the context of this paper, this work illustrates a direction in which
progress needs to be made. Firstly, it relates the behaviour of the eddy
kinetic energy, KE, to the VAI and secondly it examines the response of other,
related atmospheric parameters to the passage of an SSB. Thus, once the VAI
has been used to establish the reality of the effects we must move towards
the use of other meteorological parameters.
k. CONCLUSIONS
We have seen that it is dangerous to use the statistical sun-weather
effects that are available at present as forecasting tools. Either a well
understood physical mechanism or else a phenomenological, one-to-one relation-
ship which satisfactorily allows for seasonal and longer term variations is
needed. Since a satisfactory physical coupling has so far proved to be so
elusive, it seems probable that such a one-to-one relationship is a necessary
step towards establishing such a model. Therefore, it is concluded that
further statistical studies are required before either the "academic" or the
"economic" goal is achieved. These statistical studies must be well conceived
in order to result in a detailed description of both the morphology of the
results and the behaviour of such meteorological parameters as can be readily
incorporated into prognostic models.
Therefore, we conclude that the answer to the question posed in the intro-
duction is a qualified yes. The "economic" goal can, in principle be
satisfactorily achieved without first fulfilling the "academic" goal completely
but not until further work has been performed. Moreover, it seems probable
F - 91
that the "economic" goal provides the most likely route to the "academic" one.
Finally, both goals are most likely to be achieved by a concerted effort
aimed at fully understanding a particular sun-weather effect, such as the one
considered in this paper.
ACKNOWLEDGMENTS
RGW wishes to thank the United States - United Kingdom Educational
Commission whose financial support made much of this work possible.
REFERENCES
Dutton, J. A., and D.R. Johnson (1967)-' The theory of available potential
energy and a variational approach to atmospheric energetics.
Advances in Geophysics, 12:333-
Hines, CO., and I. Halevy (1977) : On the reality and nature of a certain
sun-weather correlation. J. Atmos. Sci, 3*+:382.
Larsen, M.F., and M.C. Kelley (1977)* A study of an observed and forecasted
meteorological index and its relation to the interplanetary magnetic
field. Geophys. Res. Lett., ^33^.
McGuirk, J. P., and E.R. Reiter (1976): A vacillation in atmospheric energy
parameters. J. Atmos. Sci., 33 : 2079 •
Ramage, C.S. (1976): Prognosis for weather forecasting. Bull. Amer. Meteor.
Soc, 57:^.
Wilcox, J.M., P.H. Scherrer, L. Svalgaard, W.O. Roberts, R.H. Olson and
R.L. Jenne (197^) : Influence of solar magnetic sector structure on
terrestrial atmospheric vorticity. J. Atmos. Sci., 31 :58l
Wilcox, J.M., L. Svalgaard and P.H. Scherrer (1975) : Seasonal variation
and magnitude of the solar sector structure-atmospheric vorticity effect.
Nature, 255:539.
Wilcox, J.M., L. Svalgaard and P.H. Scherrer (1976): On the reality of a
sun-weather effect. J. Atmos. Sci., 33,1113-
Williams, R.G. (1978a): A study of the energetics of a particular sun-
weather relation. Geophys. Res. Lett., 5:519.
Williams, R.G., and E.J. Gerety (1978): Does the troposphere respond to day-
to-day changes in the solar magnetic field ? Nature, 275:200.
Williams, R.G. (1978b): Comments on "Large amplitude standing planetary
waves induced in the troposphere by the sun" by J.W. King et al.
J. Atmos. Terr. Phyg . , 41:643.
F - 92
G. MISCELLANEOUS PREDICTIONS
A PREDICTION OF THE INFLUENCE OF T, [NO] AND q(0 ) ON THE
POSITIVE ION COMPOSITION AT THE MESOPAUSE REGION
D.K. Chakrabarty and Purobi Chakrabarty
Physical Research Laboratory
Ahmedabad 380009, India
Usiiig a currently known detailed positive ion
chemical scheme, an attempt has been made to predict
theoretically, the effect of the variation of T, [NO]
and q(0„) on the positive ion composition at the meso
pause region.
INTRODUCTION
An accurate knowl
with height in the D r
power and frequency of
the long distance radi
Several Government Dep
Communication, Defence
simplest way to„obtain
relation q =°^N where
is the effective elect
this method depends on
While subject to certa
value of q to a good d
value of oC is not that
relative densities of
exist in that conditio
of our interest, 80 -
positive ion species t
Positive ion comp
groups in different ge
1978; Goldberg and Wit
Narcisi, 1973) . These
and extent of the vari
that a variation of ei
meters viz. T, tempera
the electron-ion produ
place during these eve
To predict the variati
tion, one has to eithe
scheme. Although the
edge of electron density
egion is necessary to kn
a transmitter that one
o communication via the
artments like the Post 0
, etc. need this informa
the value of Ne is to u
q is the electron produ
ron loss coefficient. T
how accurate are the va
in conditions, one can c
egree of accuracy, the c
simple. It depends cri
positive and negative io
n in the D-region. In t
90 km, it is the concent
hat are important,
osition has been measure
ophysical conditions (Me
t, 1977; Arnold and Kran
observations have revea
ation of these ions. It
ther one or more of the
ture, NO, nitric oxide d
ction rate due to ioniza
nts (Offermann, 1977; Th
on of these parameters w
r use a simplified schem
simplified scheme has so
, Ne
ow th
has t
ionos
f f ice
tion .
se th
ction
he ac
lues
alcul
alcul
t ical
n spe
he he
ratio
dis tr i
e valu
o empl
phere .
, Over
The
e well
rate
curacy
of q a
ate th
ation
ly on
cies t
ight r
ns of
but ion
e of
oy for
-seas
-known
and cC
of
nd oG •
e
of the
the
hat
egion
d by several
ister et al . ,
kowsky, 1977;
led the nature
has been found
following para-
ens ity and q (0 ~ ) ,
tion of 0 j takes
rane et al. , 1978)
ith ion composi-
e or a detailed
me basic
1
advantages, like fewer parameters, it does not give any indepth
understanding. A detailed scheme is, therefore, always
desirable. But, unfortunately the reaction rates for this
situation are not fully known. Nevertheless, one can make a
detailed study of the effect of the variation of these para-
meters on the D-region positive ion composition by assuming
reasonable values for the unknown rate constants from the
analogous reactions (Thomas, 1976; Reid, 1977). Such an
attempt has been made in this report. The detailed ion
chemical scheme which we have used here, has been able to
satisfy the quiet time D-region features (Chakrabarty et al.,
1978). By imposing different constraints on the scheme, we
have predicted the variation of positive ion composition at
the mesopause region. The constraints are a) an increase of T,
b) an increase of q(0„) and c) an increase of NO density and
hence q (NO) .
2. TECHNIQUE
The ion-chemical scheme which we have used in this study
is shown in Figure 1, alongwith the rates, the references of
' ■■■$:>
Ih'ih^x}
37 38 Jh'iHjOIjXI
O |H(H20)4X|
Rl « R9 « Rl 5 = 2.5 x 10-29(200/T)2 [C02] [N2]
R2 - RIO = R16 = 2.0x 10-31(300/7V 4 [N2] [N2]
R3- 1.1 x 10-g(300/T)44exp(-2125/D[N2]
R4-R12-R18=1.0xl0«[CO2]
R5-R13-R19=1.0xl0»[H2O]
R6-R14 = R20=1.0xl0-9[H2O]
R7-1.0xl0-'*[N2 + O2]
R8-7xlO-,2[H]
R11-R17-10R3
R21-3.3xl0-,o[H2O]
R22-R23-10R7
R24 = 4.4x10 ,0[NO]
R25=1.0xlO,7[N2]
R26 = 2.4 x lO-^OOO/T)' 2 [O,] (0,1
R27 = 3.0xl0,ofOl
R28 = 2.2xl0"[H2O]
R29 = 0.6 (photodetachment)
R30=l.9xl0*[H2O]
R31=3.0xl0-,o[H2O]
R32 = 3.2xl0*[H2O]
Ul = 2.5 x 10" [Nj + Ojl'OOO/T)4''
U2=1.0xl0*[H2O]
Figure 1. SCHEMATIC DIAGRAM OF POSITIVE ION CHEMISTRY
G - 2
whic
cont
f igu
stat
dens
sum
heig
foil
The
both
mete
The
temp
valu
T an
is v
obta
h are
inui ty
re are
e cond
ity, N
of all
ht reg
owed a
elect r
ma j or
rs use
comput
eratur
es con
d NO d
aried
ined a
aval
equ
sol
it io
e .
the
ion
t al
on-i
and
d ar
at io
e pr
s tan
ensi
by k
re d
labl
at io
ved
n wi
The
pos
of o
1 al
on p
min
e as
ns a
ofil
t .
ty v
eepi
iscu
e from
ns of a
s imul t a
th an a
equat io
itive i
ur inte
titudes
roduct i
or, and
descr i
re done
e is ch
In the
alues c
ng T an
ssed be
Chakrab
11 the
neous ly
rbitrar
ns are
ons (wh
rest) s
from 8
on rate
the re
bed in
in thr
anged b
second ,
ons tant
d q(02)
low .
arty e
ion sp
by a
y ini t
then i
ich is
tabili
0 to 9
s , the
mainin
Chakra
ee pha
y keep
q(o2)
. And
cons t
t al. (1
ecies sh
computer
ial valu
t erated
equal t
zes. Th
0 km in
neutral
g all o t
bar ty et
ses . In
ing NO d
is vari
in the
ant. Th
978)
own
for
e of
unt i
o Ne
e pr
2.5
con
her
al.
the
ens i
ed b
thir
e re
T
in t
a s
ele
1 N
in
oced
km s
cent
inpu
(19
fir
ty a
y ke
d, N
suit
he
his
teady
ctron
, the
the
ure is
teps .
rations ,
t para-
78).
st, the
nd q(02)
eping
0 dens ity
s thus
3. RESULTS AND DISCUSSION
3.1 Variation of T
A c
observed
absorp t i
1978, Th
(Schmidl
of varia
and [H .
is seen
[NO .H20
This is
the rate
decrease
of [NO .
T at 90
at this
electron
number o
be produ
2C) is d
fewer nu
shows ho
ture. T
80 km wh
hang
dur
on ,
eon
in,
tion
(H20
that
]/[N
unde
R2
s ve
H20]
km a
alti
s be
f NO
ced .
ue t
mber
w th
his
en T
e in
ing c
noct i
et al
1976)
of t
>."<
as t
0 ] a
rs tan
(see
ry fa
will
nd af
tude
c.°
mes
HO
The
o two
s of
e f = l
level
= 207K
tempe
ondit
lucen
• , 19
In
emper
[N0+]
he te
nd f
dable
Figur
st .
be f
ter c
loss
the
is f
rap i
fact
H . (H
leve
lies
ratu
ions
t cl
67)
Fig
atur
+ [
mper
deer
bee
e 1)
Cons
orme
erta
of
ma j o
orme
d de
ors .
go
re at th
like wi
oud (Off
as well
ures 2A ,
[NO
at
eon
Op) (he
acure in
ease and
ause as
which i
equent ly
d. The
in tempe
NO by d
r loss p
d , less
crease o
Firstl
ions ar
es down
8 5 km wh
e me
nter
erma
as i
B a
• H
rear
crea
tha
the
s pr
, mo
incr
ratu
isso
roce
numb
f f
y, [
e f o
with
en T
sopau
anom
nn , 1
n qui
nd C
0]/[N
ter c
ses ,
t of
tempe
opor t
re of
ease
re , i
ciati
ss of
er of
wi th
NO] i
rmed .
the
= 175K
1 has been
lar cap
rane et al . ,
it ions
wn the effect
0 +]/[0,]
). It
ues of
0„ ] increases .
increases ,
and less
]/[0 ] with
nal because
mbination with
Since less
se leve
aly, po
977; Th
et cond
are sho
0+], [N
ailed f
the val
[N0+]/[
rature
ional t
[N0+]
of [NO
s margi
ve reco
NO .
H . (Ho0) will also
* n
ture (Figure
tempera
ncrease
Figur
increas
, and s
s and secondly ,
e 2C also
e of tempera-
lides to
3.2 Variation of q(0«)
A change in the value of q(0~) takes place during events
like PCA, aurora, solar flare and solar eclipse. The degree
of change depends on the severity of the event. In Figures 2D,
G - 3
10'
10°
.0"'
10*
T T -
•v (C)
\80KM
\85KM ^V
'
' 1
10'
10 -
10-
10"'
_J ' (F)
:r^-
BOKM^V.
85KMX.
1 1
i i i
(B)
10*
BO KM
yS 85 KM
■
10'
■^ 90KM
irP
r" i l
1
i
(E)
10'
-
10°
-
I0H
i ^
140 170 200 230 260 I 10 100 1000 " I 10 100
TEMPERATURE (K) FACTOR BY WHICH FACTOR BY WHICH
q(02) IS INCREASED q(NO)IS INCREASED
Figure 2.
A,B,C: VARIATI
[H+.(H 0) ] /
RATURE WHEN
D,|,F
VARIATI
[H" .(HO) ] /
WHEN T AND
ON OF
([N0+
q(02
ON OF
([N0 +
[NO]
G,H
[H+
(HO)]
WHEN T AND
VARIATION OF
([N0 +
q(02)
/
E an
[NO*
[NO
q(o2
incr
ther
An i
reac
[NO
from
cons
d F a
] > [NO
• HO]
) Inc
ease
e wil
ncrea
t ion
.HO]
Figu
tant
re shown
]/[0+] a
/[N0+^],
reases .
of q(0.) ,
1 be a de
se of [02
R24 (see
/[NO ] ra
re 2D, at
upto the
the ef
nd f .
[N0+]/
This i
more
crease
] will
Figure
tio sh
80 an
point
feet
4 i
[o2]
s und
02 io
in t
also
1 )
ould
d 85
when
[NO .H20] / [NO ], [NO ]/[0 ] AND
]+[02]) RESPECTIVELY WITH TEMP-
) AND [NO] ARE CONSTANT.
[NO* HO] / [N0+] , [N0+]/[0*] AND
]+[0 ]) RESPECTIVELY WITH q(02)
ARE CONSTANT.
[NO* HO] / [N0+], [N0+]/[02] AND
]+[02]) RESPECTIVELY WITH q(NO)
ARE CONSTANT.
of variation of q(02) on [NO .HO]/
s seen that the values of
and f decrease as the value of
erstandable because with the
ns will be formed. As a result,
he values of f and [NO ]/[02].
increase [NO ] through the
and hence [H (H20) ] . Thus the
apparently remain constan*". But
km we find that this ratio remains
the value of q(0«) is increased by
a fact
ratio
and at
the di
transf
that t
in the
compar
temper
km to
about
when s
has be
altitu
intere
below
factor
decrea
throug
or of 1
starts
90 km
s sociat
er thro
he chan
value
ed to t
ature (
80 km,
500 fro
uch an
en foun
de of a
sting p
80 km,
of 10
sing pr
h disso
0 from
decreas
the los
ive rec
ugh the
ge in t
of q(02
hat whi
see Fig
an incr
m that
increas
d to co
bout 70
oint to
f remai
from th
obably
ciat ive
that
ing.
s of
ombi
rea
he f
).
ch t
ure
ease
of n
e in
me d
km
be
ns c
at o
due
rec
of nor
This
[NO .H
nation
ct ion (
= 1 le
But the
akes pi
2C) . T
in the
ormal v
q(o2)
own muc
(Arnold
noticed
ons tant
f norma
to the
ombinat
mal
happ
with
10).
vel
mag
ace
0 lo
val
alue
take
h be
and
fro
unt
1 va
incr
ion
valu
ens
star
ele
A
take
nitu
due
wer
ue o
is
s pi
low
Kra
m Fi
il q
lue ,
ease
with
e , bey o
because
ts pred
ctrons
look at
s place
de of t
to a ch
the f =
f q(02)
neces sa
ace , th
80 km,
nkowsky
gure 2F
(02) is
beyond
d loss
electr
nd w
aft
omin
ins t
Fig
due
his
ange
1 1
by
ry.
e f
almo
, 19
is
inc
whi
of t
ons .
hich
er t
antl
ead
ure
to
chan
in
evel
a fa
In
= 1
st t
77).
that
reas
ch i
his
thi
his
y th
of c
2F s
a ch
ge i
the
fro
ctor
an e
leve
o an
An
at
ed b
t st
ion
s
limit
rough
harge
hows
ange
s less
m 85
of
vent
1
other
and
y a
arts
3.3 Variation of NO density
Th
change
(Arnold
quiet c
the val
[NO .H2
are sho
[NO .H2
increas
increas
[N0+]/[
decreas
probabl
ions by
shows t
ratio b
that th
An incr
this le
+ A
[NO ,H2
q(02) a
tempera
A
ratio i
density
very mu
A
with th
of this
e density of NO a
during conditions
and Krankowsky,
onditions. A cha
ue of q(N0) . The
0]/[N0 *], [N0+]/
wn in Figures 2G,
0]/[N0 ] and f de
e with the increa
e s , more NO will
0„ ] ratio and a d
e of [NO .H20]/[N
y due to the incr
dissociative rec
hat a 10 time inc
y almost the same
e f = 1 level goe
ease of NO densit
vel down to 80 km
comparison of Fig
0] / [NO ] decrea
nd [NO] , the rati
ture than q (0« ) a
comparison of Fig
ncreases with inc
but decreases wi
ch sensitive to c
comparison of Fig
e increase of T ,
decrease is more
t th
lik
1977
nge
e|f
[oZ]
Ha
crea
se o
be
ecre
0+]
ease
ombi
reas
f ac
s do
y by
e mes
e aur
; Off
in th
ects
and
nd I.
se an
f NO
forme
ase o
ratio
d eff
natio
e in
tor .
wn wi
a fa
opau
ora ,
erma
e va
of v
[H .
We
d th
dens
d, h
f f
wit
ect
n wi
[NO]
Fro
th t
ctor
se h
win
nn ,
lue
aria
(HO
fin
at o
ity.
ence
are
h in
of t
th e
inc
m Fi
he i
of
as b
ter
1977
of N
tion
dnth
f [N
As
an
unde
crea
he 1
lect
reas
gure
ncre
4 at
een found to
anomaly et c .
) from that of
0 will also change
of q(N0) on
([NO +]+[0;])
at the values
0+] / [op
NO density
of
of
increase
rs tandable .
se of
oss
The
[NO] is
of NO .HO
rons . Figure 2H
es [N0+]/[02]
21 it is seen
ase of NO density.
85 km can bring
ures 2A, D and G shows that although
ses with the increase of temperature,
o is more sensitive to changes in
nd q(N0) .
ures 2B, E and H shows that [NO ]/[02]
rease of temperature and nitric oxide
th increase in q(0~). The ratio is
hanges in nitric oxide.
ures 2C, F and I shows that f decreases
q(0„) and NO density. But the magnitude
sensitive to T and NO variations than
q(0„). An increase of temperature by about 30K can bring the
f = 1 level from 85 to 80 km. Similarly an increase of NO
density by a factor of 4 can also bring the f = 1 level from
85 to 80 km. Does this indicate that there is a link between
T and NO values?
4. CONCLUSION
The dependence of the positive ion composition on
temperature, nitric oxide density and electron production rate
due to the ionization of 0„ at the mesopause region is studied
It is shown that to predict the electron density in the meso-
pause region, effectively, there is an urgent need of more
accurate and reliable measurements of temperature and nitric
oxide density along with reliable electron production rates
for different conditions of the ionosphere at all latitudes.
REFERENCES
Arnold, F., and D. Krankowsky (1977): Ion composition and
electron-and ion-loss processes in the earth's atmosphere.
Dynamical and Chemical coupling between the Neutral and
Ionized Atmosphere, -.93.
Chakrabarty, D.K., P. Chakrabarty, and G. Witt (1978): An
attempt to identify the obscured pathj of water cluster
ions build-up in the D-region. J. Atmos. Terr. Phys., 40:
43 7. ■
Goldberg, R.A. , and G. Witt (1977) : Ion composition in a
noctilucent cloud. J . Geophys . Res . , 82:2619.
Meister, J., P. Eberhardt, U. Herrmann, E. Kopp, M.A. Hidalgo
and C.F. Sechrist, Jr. (1978): D-region ion composition
during the winter anomaly campaign on January 9, 1977.
Space Res . , XVIII;155.
Narcisi, R.S. (1973): Mass spectrometer measurements in the
ionosphere . Physics and Chemistry of Upper Atmosphere , j 1 7 1
Offermann, D. (1977): Some results from the European winter
anomaly campaign 1975/76. Dynamical and Chemical coupling
between the Neutral and Ionized Atmosphere , : 2 3 5.
Reid, G.C. (1977): The production of water cluster positive ions
in the quiet daytime D-region. Planet . Space Sci . , 2 5:275.
Schmidlin, F.J. (1976): Temperature inversion near 75 km.
Geophys . Res . Lett . , 3:173.
Theon, J.S., W. Nordberg, L.D. Katchen, and J.J
Some observations on the thermal behaviour
mesosphere, J . Atmos . Sci . , 24:428.
Horvath (1967)
of the
Thomas, L. (1976): Mesospheric temperatures and the formation
of water cluster ions in the D-region. J . Atmos . Terr .
Phys .,38:1345.
Thrane, E.V., W. Bangert, D. Beran, M. Friedrich, B. Grandal,
0. Hagen, A. Loidt, K. Spenner, H. Schwentek, K.M. Torkar,
and F. Ugletveit (1978): Ion production and effective
electron loss rate in the mesosphere and lower thermos-
phere during the Western Europe Winter Anomaly Campaign
1975-76. J. Atmos. Terr. Phys., (in press).
G - 7
ON PREDICTING THE PARAMETERS OF MEDIUM SCALE GRAVITY
WAVES WITH THE ONSET OF TROPOSPHERIC JET STREAM
0. P. Nagpal
Department of Physics, University of Nairobi
P.O. Box 30197, Nairobi, Kenya
Dynamic instability of the wind shear layers in the
tropospheric jet stream can generate short and medium
scale gravity waves. Using the meteorological data and
some reasonable models for the jet stream, various para-
meters of the generated gravity waves like speed, direc-
tion, period and horizontal wavelength can be predicted.
No claim is made of the originality of the results pres-
ented here as several of these have already appeared in
the recent literature. The emphasis has been to indica-
te that this analysis can be used as a prediction tech-
nique for the regularly occurring type of gravity waves
both in the lower atmosphere and in the thermosphere.
1 . INTRODUCTION
Earth's atmosphere is characterised by the presence of atmospheric
gravity waves which occur with a wide range of periods, wavelengths and
propagation speeds. Of the several phenomena of the atmospheric dynamics
which these waves explain, the most established is the phenomenon of
travelling ionospheric disturbances (TIDs) . One of the interesting
features of the gravity waves observed both in the neutral and ionised
components of the upper atmosphere is their downward vertical phase
propagation. Hines (1960) has pointed out that this sense of the phase
progression implies that the wave sources must generally lie below the
height of observation. Gossard (1962) confirmed Hines' suggestion and
found that for an atmosphere without background wind, a window can exist
at periods of about 10 min to 2 hr through which substantial amount of
energy can leak out of the troposphere and this in turn may account for
the frequent occurrence of the medium scale TIDs in the thermosphere.
Since then, many investigators have turned their attention to meteorolo-
gical sources of gravity waves which include weather frontal systems,
severe thunderstorms, instabilities and distortions in the jet streams
and penetrative cumulus convection. Once upper air data became routinely
available, it was observed (e.g. Flauraud et al., 1954; Madden and
Claerbout, 1968; Herron and Tolstoy, 1969; Herron et al., 1969) that many
cases of gravity waves move with velocities that match the jet stream
winds directly above. Based on these findings, Madden and Claerbout
G - 8
(1968) and Tolstoy and Herron (1969) suggested that these waves can be
produced by wind shear layers within the jet stream. Mechanisms include
static instability (local convective activity) and dynamic instability
(reduction in Richardson number within shear layers). Generation of
wave spectra by both mechanisms has been examined by Tolstoy (1973).
There is, however, a recent evidence that out of the two mechanisms,
dynamic instability associated with vertical wind shear layers may be the
chief cause for the generation of gravity waves (Keliher, 1975; Gedzelman
and Rilling, 1978). Hence predictions may be made as to gravity wave
period, speed and direction if the information concerning the wind shear
layer is available.
Recently, evidence has also emerged by way of reverse ray tracing
technique that some of the regularly occurring type of medium scale TIDs
have their origin in the tropospheric jet stream (Cowling et al., 1970;
Goe, 1971; Bertin et al., 1975, 1978; Sengupta et al., 1977: Sizun and
Bertel, 1978) although the inferences are not free from difficulties.
However, if each wave is considered separately and if efforts are made to
get a complete wind profile upto the thermospheric heights, the character-
istics of the observed TIDs can be matched with those predicted.
In the present paper, an attempt has been made to obtain information
concerning the nature and characteristics of short and medium scale gravity
waves (period, wavelength, speed and direction) generated by the onset of
a tropospheric jet stream in the atmosphere. A brief description of the
jet stream is given in section 2. The analysis given in section 3 is
based on the previous studies of this kind by many investigators (e.g.
Tolstoy and Herron, 1969; Keliher, 1975; Lalas and Einaudi, 1976;
Mastrantonio et al., 1976). Section 4 gives the comparison of the predi-
cted and observed gravity wave parameters.
As the tropospheric jet streams are regular features of the atmosphere,
they would well account for the day to day observability of gravity waves
both below and above the troposphere. Apart from whatever interest gravity
waves attract in themselves or as a remote indicators of the other impor-
tant geophysical phenomena, increasing attention is being paid to know
how much energy and momentum these waves can carry when they propagate to
upper atmosphere. This can be made possible by developing an ability to
measure and model the various wave parameters originating from a given
source. Also there is a current belief that clear air turbulence (CAT)
is correlated with gravity waves observed at the ground level. However,
the gravity waves that might be most effective in causing CAT have much
smaller wavelengths than the ones either seen on microbarographs or
higher in the atmosphere. Since, an unstable shear layer produces a
spectrum of wavelengths the smaller of these might produce CAT and the lar-
ger of these might produce other effects.
2. DESCRIPTION OF JET STREAM
An atmospheric jet stream is described as a high speed air current in
the form of a flattened, narrow core or tube, thousands of km in length,
a hundred or more km in width, and one or more km in vertical thickness.
Although reports of maximum winds in the centre of the core reach 300
knots (150 m/sec) 100 to 200 knots (50 to 100 m/sec) is more typical of the
maximum jet winds encountered. These maximum winds usually occur between
10-12 km but jet winds of lesser magnitude may be found at times above 6
km. There are two basic jet streams in the troposphere - the polar front
jet stream (PFJ) and subtropical jet stream (STJ). The mean position of
these jets for winter is shown in Fig. 1. During the winter, the STJ is
polor Tropopo"««
horizontal mixing
weak »ubsidence
L
90°
SO-
SO-
<r
Latitude
Fig.l. SCHEMATIC REPRESENTATION OF THE MEAN
MERIDIONAL CIRCULATION IN THE NORTHERN HEMI-
SPHERE DURING WINTER. HEAVY LINES= TR0P0PAU-
SES AND POLAR FRONT. PFJ= POLAR FRONT JET
STREAM AND STJ= SUBTROPICAL JET STREAM.
(AFTER PALMEN, 1954).
relatively constant and continues "in position and time and becomes broken
and weak during the summer months. When well developed, winds of more than
150 knots (75 m/sec) are not uncommon. The PFJ is much more variable in
location, continuity, wind speed and elevation. It is farthest south in
mid winter and farthest north in summer, and its elevation decreases as it
migrates northward. Both these jet streams are characterised by well-
marked horizontal wind shears and strong vertical wind shears. Also wind
speeds in the jet stream can build up only to a certain limiting value,
beyond which cyclonic shears would be generated that produce dynamic inst-
ability (minimum Richardson number).
2.1 Jet Stream Associated Waves
One of the long established observations of surface pressure fluctua-
tions interpreted as gravity waves is that the observed wave speeds and
directions bear a relation to the speed and orientation of the upper atmos-
pheric jet stream. Such correlations have been noted by many investigators
(Flauraud et al., 1954; Madden and Claerbout, 1968; Herron and Tolstoy,
1969; Keliher, 1975; Essex and Love, 1978; Gedzelman and Rilling, 1978).
The pressure oscillations tend to be of relatively low frequency (5-20 min
periods) and the horizontal trace velocities are in the range of 20-60 m/sec
10
i.e. comparable to that of the jet stream. The association of these waves
with the upper tropospheric jet stream now seems to be well documented, but
the nature of connection remains unclear. However, there is recent evide-
nce (Hooke and Hardy, 1975; Gedzelman and Rilling, 1978; Essex and Love,
1978) from surface pressure and clear-air radar observations which tend to
confirm the suggestion by Madden and Claerbout (1968) that the wave gene-
ration mechanism in the troposphere may be dynamic instability associated
with vertical wind shear in the neighbourhood of the jet stream. Goe
(1971) inferred a casual connection between TIDs with periods of 12-15 min
observed at Boulder and jet stream configurations with large horizontal
wind shears. Cowling et al. (1970), and Bertin et al. (1975) using reverse
ray tracing technique through windy atmosphere reported that weather
disturbances and jet streams appeared as likely sources for the medium
scale F region TIDs. Similar conclusions were drawn by Sengupta et al.
(1977) who noted that the winter time medium scale TIDs correlated well
with the westerly jet stream activity.
This correspondence has provided one of the principal form of evidence
which supports the idea that the waves are generated by the dynamic inst-
ability of the jet stream winds.
2.2 Excitation of Gravity Waves
The excitation of gravity waves by shear flow instability has been
investigated extensively. Drazin and Howard (1966) have presented a
thorough review of the theoretical work in hydrodynamic stability of plane-
parallel flow up to that time. The primary aim of these investigations is
to specify, for given velocity and density or temperature profiles, the
characteristics of the most unstable wave to be excited i.e. its wavelength,
period, phase velocity and growth rate, as well as the range of horizontal
wavelengths Xx that are unstable for a given value of some characteristic
Richardson number of the flow. Drazin and Howard (1966) show that for a
homogeneous fluid with a monotonic velocity profile, a necessary condition
for instability is that the velocity profile should have an inflection
point. In such a fluid the waves will travel with a speed and direction
matching that of the fluid at the inflection point. In a stratified fluid,
however, there is no general expression for the wave speed although it is
restricted to lie within the range of wind speeds by Howard's (1961) semi-
circle theorem. The above analysis predicted the existence of one mode
only which was connected with singular neutral solution.
More recently Jones (1968) discovered that there are other unstable
modes which are not connected with the singular neutral solution. These
new modes generally have longer wavelengths, are weakly dispersive and
may not necessarily move with velocity of the fluid at the inflection
point. These new modes have also been investigated by
Lalas and Einaudi (1976), Davis and Peltier (1976) and Mastrantonio et al.
(1976). Although these linear theories do suggest that an atmospheric
shear layer can support a number of unstable modes in agreement with the
observations (Hooke and Hardy, 1975), however, the generation of medium
scale gravity waves which are observed at the F region heights is
G - 11
forbidden in such linear theories. Paul (1977) and Bertin et al . (1978)
point out that such waves may not be produced directly by shear instability
but rather may result from non-linear interaction of two smaller, unstable
waves. This theory has been able to account for certain of the observed
characteristics of the internal gravity waves observed at the thermospheric
heights.
3. PREDICTION OF GRAVITY WAVE PARAMETERS
3.1 Speed and Direction
The following method as outlined by Keliher (1975), will be used to
predict the gravity wave speed and direction. The basic data required is
the wind speed and direction as obtained by radiosonde and the temperature
profile. It is first essential to identify the height at which the shear
layers are present within the jet stream. This can be done by calculating
the Richardson number which is given by
2
where _9ju is the vertical shear of the wind in the horizontal direction
and N is the Brunt Vaisalla frequency defined by
(1)
NB - <*'«> H
(2)
where g i's the gravitational acceleration and 8 is the potential temperature,
Knowing the data for two adjacent radiosonde sounding at levels z. and z„,
one can calculate the approximate Richardson number from the following:-
[
(g/c
T2"
- z
-)
u since- - u.sinct. 2
( ■ --, ) *
u cosa„ - u.cosa. 2
(— T-TT- — )
z2 zi
-l
(3)
where T., u. , a. are temperature, wind speed and direction at height z. and
T«, u„, a are corresponding quatities at level z?. c is the specific
heat at constant pressure. The height level where R.< | can then be chosen
as the level where shear instability would be present (Chimonas, 1970).
If v. and v_ are the horizontal winds at two heights z. and z~ immediately
below and above the level where R.^i and assuming that wind varies in a
linear manner between these levels, one may expect the gravity waves
produced by such a region to travel with speed
12
A . A A
vm = Uv, + v2) (4)
relative to the ground and to have wave fronts perpendicular to
Vs = V2 - vl (5)
zl + z2
As the source is located at an average altitude z (= 5 ) the gravity
waves over an array located at some horizontal distance x from the source
will have an observed velocity v given by (Essex and Love, 1978)
v = |v |cos(v ,v ) / cos tan (z/x) (6)
o ' m' m' s
and azimuth given by
-1 /2Sina2 ~ vlslnalN (7)
a = tan ( )
s v cosa - v.cosa.
Equations (6) and (7) allow us to calculate the predicted apparent speed v
and azimuth a of any wind shear generated wave.
Since radiosonde soundings are usually made every 12 hours, each sounding
can be assumed to be a measure of meteorological conditions for 6 hours
before and 6 hours after the time of release. As noted in section 2, STJ
is relatively constant and continuous in position and time during winter
months, the above equations can therefore be used to get the gravity wave
speed and direction generated by STJ.
3.2. Period and Wavelength
To obtain the periods and expected horizontal wavelengths of the jet
stream generated gravity waves, one has to resort to the modelling approach.
Of the wind profiles utilised to model a shear layer, the simplest is the
Helmholtz profile which has a background horizontal velocity U (z) constant
in each of two semi-infinite media and a sharp discontinuity at the
separating interface. Other models in use are constant velocity layers and
U (z) given by a hyperbolic tangent profile (Drazin, 1958; Maslowe and Kelly,
1971; Thorpe, 1973). One then does the stability analysis of such an
idealised model of a jet stream shear layer and the characteristics of
the most unstable modes are calculated for minimum Richardson number of the
flow. The stability investigations are usually supplemented by the general
stability results of Miles (1961), Howard (1961) and Chimonas (1970) that
provide bounds on the range of the phase velocities and growth rates of the
unstable waves through the Howard's semi circle theorem.
Using the hyperbolic-tangent velocity profile for the atmospheric shear
layer of the form U (z) = V tanh(z/h) shown in Fig. 2, where V is the
maximum value of the background wind velocity U at z = h the height of the
tropopause, and constant background temperature, Lalas and Einaudi (1976) and
G - 13
i~lt/v
Fig. 2. THE NORMALISED DENSITY AND
VELOCITY PROFILES AND THE GEOMETRY
OF THE BASIC FLOW IN THE TROPO SPH-
ERIC JET STREAM (AFTER LALAS AND
EINAUDI,1976).
Fig. 3. REPRESENTATION ON AN (w,kx)
DIAGRAM OF THE UNSTABLE MODES ABLE
TO DEVELOPE IN A JET STREAM WITH
MAXIMUM VELOCITY V= 60 m/sec AND
MINIMUM RICHARDSON NUMBER J=0.1.
THE UPPER AND LOWER DIAGRAMS CORRES-
POND TO THE IMAGINARY (GROWTH RATE)
AND REAL PARTS OF m. THE NON-LINEAR
INTERACTION BETWEEN WAVES 1 AND 2
OR 1 AND 3 CAN YIELD WAVES WITH VAL-
UES OF u AND kx WITHIN THE RANGES
SHOWN FOR WAVES OBSERVED IN THE
THERMOSPHERE (AFTER BERTIN et al.,
1978).
I Propaga ting mode,
II jik! III «rs Trapped modes
J = 0.1
,-4_-t
k. 10 "V
G - \h
Mastrantonio et al. (1976) find that the tropospheric jet stream can support
a number of modes, some of which are essentially evanescent and others
essentially free, propagating away from the shear zone. Figure 3 represe-
nts these unstable modes in an (w,k ) diagram calculated by Bertin et al.
(1978) from the work of Lalas and Einaudi (1976) for a jet stream located
at 12 km height and having maximum core speed of 60 m/sec. This gives us
the expected horizontal wavelengths for a particular to (or period) of a
gravity wave mode. For example mode labelled I is a freely propagating
mode capable of travelling upto thermospheric heights. The expected
wavelengths would be 50 km or more. Wavelengths of the order of ten as
well as few hundred kilometers have been recently detected by Uccellini
(1975) which were thought to be responsible for triggering various kinds of
atmospheric events along their path (e.g. convective thunderstorm). How-
ever, observations of medium scale gravity waves by Bertin et al. whose
source origin was believed to be a jet stream, give characteristics which
do not match with any of the modes shown in Fig. 3. Thus they suggest that
the observed wave could arise due to non-linear interaction of the two
trapped modes labelled II and III. Similar analysis has been given by
Paul(1977) who shows that the resulting wave from non-linear interaction
of the smaller, unstable waves can account for certain of the observed
characteristics of the power spectrum of the waves. The waves thus produced
are internal waves which can travel freely through the fluid.
Similarly, in the lower atmosphere, pressure fluctuations at the ground,
with periods of few minutes to several minutes and horizontal wavelengths
of tens of meters to a few hundred kms were successfully explained by
Tolostoy and Herron (1969) to originate in the jet stream. They computed
the spectral distributions of gravity waves as would be expected on the
ground due to disturbances of known spectra in the jet stream aloft.
The input parameters were the wind velocity power spectra obtained by
Fig. 4. THE LONGITUDINAL POWER SPECT-
RUM FOR LONGITUDINAL WIND VELOCITY
FLUCTUATIONS NEAR THE JET STREAM
CORE AS DETERMINED BY KAO AND WOODS
(1964).
WAVE NUMBER, k, (CYCLES km
15
aircraft measurements along jet stream axis by Kao and Woods (1964) and are
shown in Fig. 4. Assuming thsese spectra to be stationary and as a frozen-
in property of the wind system carried along by the jet core, Tolstoy and
Herron showed that the power spectrum for ground level pressure perturba-
tions P(p) can be computed by
P(p) = 0.2 V2 r~ P(U)
(8)
where P(u) is the power spectrum of the winds in the jet stream and is
related to Ess(k) of Kao and Woods by P(u) = kEss with k in cycles/km, v is
the iet core speed and k and k are the vertical wavenumbers at the jet
7 Z S
stream height and at the surface respectively. The spectrum thus calculated
gives acceptable orders of magnitude for some of the observed properties
of the mesoscale fluctuation fields (Hooke and Hardy, 1975). Although the
primary purpose of the above analysis is to get the amplitudes of the
surface pressure perturbations, nevertheless, the analysis does give the
various periods of gravity waves reaching the ground.
4. COMPARISON OF OBSERVED AND PREDICTED PARAMETERS
Number of investigarors have made comparison of the observed wave phase
s to
I "
~ «0
a Jit
V
oa°
'A*
°° 0o«S?
o 0 ♦ o°
I - •• \ IF • T7 • j
IzA I i I I I X/aa I Lj I i i i-
■ ■ a
DECEMBER 1971
10 I M
JANUARY 1972
H
1
•*':«$£
15 »
FEBRUARY 1972
IS N
IARCH 1972
Fig. 5. COMPARISONS IN SPEED AND AZIMUTH OF MICR0BAR0GRAPG-DETECTED
GRAVITY WAVES (PLUSES) , UPPER-TROPOSPHERE WIND MAXIMA (OPEN CIRCLES) AND
PREDICTED WIND SHEAR INDUCED GRAVITY WAVES (SOLID TRIANGLES) FOR THE
WINTER MONTHS, 1971-72 NEAR BOULDER, COLORADO. (AFTER KELIHER, 1975).
G - 16
speed and direction with the wind speed and direction of the maximum tropo-
spheric winds and good agreement has been reported. However, a comparison
between the observed wave speeds and directions with those predicted by
shear layer analysis has been attempted by a limited number of workers.
Keliher (1975) noted that best correlation existed between gravity wave
events and predictions from wind shear data during winter months (Fig. 5)
although the agreement was not too good for other months. The results of
comparison indicated that one third to one half of his observed wave events
were shear-induced. Gedzelman and Rilling (1978) and Essex and Love (1978)
have presented a similar comparison. The procedure followed is much the
same as described in section 3.1. Gedzelman and Rilling noted that about
37.5% of all the cases observed matched well both in speed and direction,
though the discrepency was small for the other 60% of the cases. This they
atrributed partly to the uncertainties involved in the radiosonde data.
Their results are reproduced in Fig. 6. From their results of comparison,
these authors concluded that shearing instability is one of the more common
generating mechanism of the waves. This conclusion was further supported by
the fact that the observed waves were not very dispersive. Essex and Love
10 15 20
NOVEMBER 1969
10 IS 20
DECEMBER 1969
Fig. 6. COMPARISONS IN SPEED AND DIRECTION OF MICRO BAROGRAPH- DETECTED
GRAVITY WAVES (PLUSES) AND PREDICTED WIND SHEAR INDUCED GRAVITY WAVES
(TRIANGLES) FOR THE WINTER MONTHS, 1969 NEAR NEW YORK (AFTER GEDZELMAN
AND RILLING, 1978) .
noted that some of their observed gravity wave speeds had the right order
of magnitude when compared with the predicted values provided that an
assumption is made for the waves to originate in the lowest unstable layer
in the jet stream.
A comparison of the observed spectra of surface pressure fluctuations
and that derived from the wind velocity power spectra of the jet stream
was made by Tolstoy and Herron (1969) who noted that a simple linear model
predicts the correct order of magnitude and power spectra for surface
pressure fluctuations in the 5-60 min period range.
G - 17
We now: carry out a comparison of the observed characteristics of the
thermospheric medium scale gravity waves with those predicted theoretically
by the jet stream model described in section 3.2. Such a comparison has
been made by a rather limited number of investigators notable among them be-
ing Bertin et al. (1978) and Vidal-Madjar et al . (1978). A reverse ray tra-
cing analysis is first employed to make sure that the wave path of the ob-
served gravity wave can be followed down to the tropopause level. Figure 7
shows the characteristics of the medium scale gravity waves as measured by
Bertin et al . (1978). The observed phase speeds lie in the range 80-250 m/
sec with a maximum near 130 and 160 m/sec. The corresponding horizontal
wavelengths are between 150-250 km and wave periods are between 17 and 40
min. Most of these waves could be traced back to the tropopause level there-
by suggesting a jet stream to be the source. The predicted gravity wave
modes which may develop in the jet stream are shown in Fig. 3. The main
features of these unstable modes can be summarised as follows:-
(i) the horizontal phase velocity in all cases is smaller than the maximum
speed in the jet, a consequence of the fact that modes are generated within
their critical level.
(ii) the direction of propagation is colinear with the jet stream.
(iii) of the three modes, the two most likely to grow (II and III) are
trapped modes propagating only inside the jet.
At first glance, all these characteristics are in contradiction to those
of the waves observed in the thermosphere and traced back to the tropopause,
where the horizontal phase velocities are at least two times that of the
jet (taken 60 m/sec as maximum). However, it has been shown by Paul (1977)
and Vidal-Madjar et al. (1978) that a non-linear interaction between two
A, (km)
Fig. 7. SPECTRAL CHARACTERISTICS OF MEDIUM SCALE GRAVITY WAVES
MEASURED BY BERTIN et al . (1978). EACH OF THE WAVE IS MARKED
BY A POINT IN A (k ,k ) DIAGRAM. THE kzIS THAT FOR THE WAVE AT
15 km ALTITUDE. T^E HYPERBOLAS ARE CURVES FOR CLASSICAL DISPER-
SION. THE ESSENTIAL POINT IS THAT THE AVERAGE PHASE VELOCITY OF
THESE WAVES IS AROUND 150 m/sec (AFTER, VIDAL-MADJAR et al., ■
1978).
18
waves with characteristics (to. ,k .) and (u)9,k „) belonging to modes II and
III respectively in Fig. 3 can produce a secondary wave which then possesses
a much larger phase speed. Table I taken from the work of Vidal-Madjar
et al. shows the expected phase speeds and vertical wavelengths for the
secondary waves formed as a result of non-linear interaction of four
waves of mode II with four waves of mode III. The parameters thus
obtained for the resulting waves are in broad general agreement with the
observed characteristics shown in Fig. 7. It should, however, be noted
that the observed spectral characteristics give only a very biased in-
dication of the spectrum of real waves emitted by the jet stream.
This is because of the atmospheric filtering between 10 and 250 km
Table - I
PHASE VELOCITY (V ) AND VERTICAL WAVELENGTH (X ) FOR THE SECONDARY WAVE
p z'
Mode
k i
XI
)f,-4 -1
x 1 0 ,m
Mode
k „
x2
in"4 _1
x 1 0 ,m
X ,km
z
V ,m/s
II
6.1
III
6.3
141
226
II
6.3
III
6.5
151
231
II
6.2
III
6.5
64
140
II
6.3
III
6.6
66.5
143
altitudes which helps the waves of higher phase velocities to reach the
upper level.
5.
CONCLUSION
As noted in the introduction, the tropospheric jet streams are regular
features of the lower atmosphere. Once the information concerning their
wind shear layers is available, one can predict the parameters of both up
and down going gravity waves launched by these jet streams. In addition
to explaining the day to day occurrence of mesoscale motions, the analysis
given here can also be used to get some idea about the energy which these
waves can carry into the thermosphere. Unfortunately, the tropospheric
data are usually available every 12 hrs a day, so one has to assume that
the jet stream does not move significantly during the time when a gravity
wave is being launched. Also parameters like the tropospheric wind
speed maximum and the exact position of the jet stream are difficult to
determine with desired accuracy because the jet stream is snakelike
rather than a clearly defined point source. In spite of these limitations,
the technique presented here predicts the gravity wave parameters which
agree reasonably well with those observed in the lower and the upper
atmosphere .
19
REFERENCES
Bertin, F., J. Testud, and L. Kersley (1975): Medium scale gravity waves
in the ionospheric F-region and their possible origin in weather
disturbances. Planet. Space Sci., 23:493.
Bertin, F., J. Testud, L. Kersley, and P. R. Rees (1978): The meteorological
jet stream as a source of medium scale gravity waves in the thermo-
sphere: An experimental study. Accepted by J. Atmos . Terr. Phys .
Chimonas, G. (1970): The extension of the Miles-Howard theorem to compre-
ssible fluids. J. Fluid Mech., 43:833.
Cowling, D. H., H. D. Webb, and K. C. Yeh (1970): A study of traveling
disturbances in the ionosphere, Tech. Rep. 38, Ionos. Radio Lab.,
Univ. of 111. at Urbana-Champaign, 147 pp.
Davis, P. A., and W. Peltier (1976): Resonant parallel shear instability in
stably stratified planetary boundry layer. J. Atmos . Sci . , 33:1287.
Drazin, P. G. (1958): The stability of a shear layer in an unbounded heter-
ogeneous inviscid fluid. J . Fluid Mech. , 4:214.
Drazin, P. G. , and L. N. Howard (1966): Hydrodynamic stability of parallel
flow of an inviscid fluid. Advances in Applied Mechanics , Vol. 9,
Academic Press, 1-89.
Essex, E. A. and G. B. Love (1978): The occurrence of ground level gravity
waves in southeastern Australia as detected by microbarographs .
J. Geophys. Res. , 83:1883.
Flauraud, E. A., A. H. Mears , F. A. Crowley, Jr., and A. P. Crary (1954):
Investigation of microbarometric oscillations in eastern Massachusetts.
Tech. Rep. 54-11, Geophys. Res. Pap. 27, Air Force Cambridge Res. Lab.
Mass., U.S.A.
Gedzelman, S. D., and R. A. Rilling (1978): Short-period atmospheric gravity
waves: A study of their dynamic and synoptic features. Mon. Wea. Rev. ,
106: 196.
Goe, G. B. (1971): Jet stream activity detected as wavelike disturbances at
mid-latitude ionospheric F region heights. Pure Appl. Geophys. , 92:190
Gossard, E. E.(1962): Vertical flux of energy into the lower ionosphere from
internal gravity waves generated in the troposphere. J. Geophys. Res.,
67:745.
Herron, T. J., and I. Tolstoy (1969): Tracking jet stream winds from ground
level pressure signals. J. Atmos. Sci. , 26:266.
G - 20
Herron, T. J., I. Tolstoy, and D. W. Craft (1969): Atmospheric pressure
background fluctuations in the mesoscale range. J. Geophys . Res . ,
74: 1321.
Hines, C. 0. (1960): Internal atmospheric gravity waves at ionospheric
heights. Can. J. Phys . , 38:1441.
Hooke, W. H., and K. R. Hardy (1975): Further study of the atmospheric grav-
ity waves over the Eastern Seaboard on 18 March 1969. J. Appl. Meteor. ;
14:31.
Howard, L. N. (1961): Note on a paper of John W. Miles. J. Fluid Mech. ,
10:509.
Jones, W. L. (1968): Reflection and stability of waves in stably stratified
fluids with shear flow: A numerical study. J. Fluid Mech. , 34:609.
Keliher, T. E. (1975): The occurrence of microbarograph-detected gravity
waves compared with the existence of dynamically unstable winds shear
layers. J. Geophys. Res., 80:2967.
Kao, S. -K. , and H. D. Woods (1964): Energy spectra of mesoscale turbulence
along and across the jet stream. J. Atmos . Sci., 21:513.
Lalas, D. P., and F. Einaudi (1976): On the characteristics of gravity waves
generated by atmospheric shear layers. J. Atmos. Sci . , 33:1248.
Madden, T. R. , and J. F. Claerbout (1968): Jet-stream-associated gravity
waves and implications concerning jet stream stability. Proc. Acoustic
Gravity Waves Symp. , T. M. Georges, Ed., U.S. Govt. Printing Office.
121-124.
Maslowe, S. A., and R. E. Kelly (1971): Inviscid instability of an unbounded
heterogeneous shear layer. J. Fluid Mech. , 48:405.
Mastrantonio, G. , F. Einaudi, and D. Fua (1976): Generation of gravity waves
by jet streams in the atmosphere. J. Atmos. Sci., 33:1730.
Miles, J. W. (1961): On the stability of heterogeneous shear flow.
J. Fluid Mech., 10:496.
Palmen, E. (1954): Uber die atmospharischen Strahlstrome. Meteorol. Abhandl.
(Berlin), 2:35.
Paul, D. P. (1977): Nonlinear gravity wave-wind interactions and jet stream
gravity wave generation. Ph. D. dissertation, MIT, 112 pp.
21
Sengupta, A., O.P. Nagpal, and C.S.G.K. Setty (1977): Travelling iono-
spheric disturbances and their possible correlation with jet stream
activity. Ind. J. Radio Space Phys., September issue.
Sizun, H. , and L. Bertel (1978): Observations of medium scale atmospheric
waves from diverse measurements. Paper presented at the Symp. on
Beacon Satellite Measurements of Plasmaspheric and Ionospheric
properties, 22-25 May, 1978, Florence, Italy.
Thorpe, S.A. (1973): Turbulence in stratified fluids: A review of
laboratory experiments. Boundary Layer Meteor., 5:95.
Tolstoy, I. (1973): Infrasonic fluctuation spectra in the atmosphere.
Geophys. J. Roy. Astron. Soc, 34:343.
Tolstoy, I., and T.J. Herron (1969): A model for atmospheric pressure
fluctuations in the mesoscale range. J. Atmos. Sci., 26:270.
Uccellini, L.W. (1975): A case study of apparent gravity wave initiation
of severe convective storms. Mon. Wea. Rev., 103:497.
Vidal-Madjar, D., F. Bertin, and J. Testud (1978): Sur le jet stream
de la tropopause en tant que source des ondes de gravite observees
dans la thermo sphere. Ann. Geophys. , 34:1.
G - 22
SOLAR RELATIONSHIP AND PREDICTION OF SEISMIC ACTIVITY OF THE EARTH
Yu. D. Kalinin and V. M. Kiselev
L. V. Ki rensky Institute of Physics
Siberian Branch of the Academy of Sciences of the USSR
Krasnoyarsk, Akademgorodok, 66OO36, USSR
Annual values of the planetary released seismic energy (E)
for 1800-197** were obtained on the basis of known earthquake cata-
logues. It was found that the principal components of the E-spec-
trum obtained by Burg's maximum entropy method correspond to time
scales of about 180, 25 and 11 years. The prediction technique of
the planetary seismic activity was developed on this basis.
1. GLOBAL SEISMIC ACTIVITY OF THE EARTH
The aim of this paper is the analysis and the prediction technique of
seismic activity on the Earth. The knowledge of statistical regularities of
the temporal variations of global seismic activity is necessary for under-
standing the causes of catastrophic earthquakes and for their time predic-
t ion .
We used annual amounts of released seismic energy (E) as the characteris-
tic of planetary seismic activity. It is known that the majority of the
annual seismic energy is released when great magnitude earthquakes occur.
Therefore to obtain the series of E-values we used the data on earthquakes
with magnitudes M^.7-9 (an earthquake with M=7-9 corresponds to a released
energy E=5xl016j). The known maximum value of E is equal to 3-**3xl0i8J for
1897-
Annual values of E for 1897-197*» were found from the earthquake data
according to Richter (1958) and according to catalogues "Earthquakes in the
USSR" (1963-197*0. Before 1897 the instrumental measurements suitable for
determination of E-values are absent. Therefore, we used the data on the
number of earthquakes per year for 1 800- 1 900 according to Lomnitz (197*0 to
find the E values for the nineteenth century. The time intersection of
Lomnitz's data and instrumental data gave a conversion factor from the annual
number of earthquakes to the amounts of released seismic energy. The con-
tinuous series of annual values of E was constructed for 1800-197*+ in this
manner.
Figure 1 represents the changes of planetary seismic energy for 1800-197**.
The year-to-year changes of E are uneven and probably random, but there are
also long-term variat ions . Note that the E series thus obtained differs from
the E series obtained by Anderson (197**)- This difference concerns the E-data
for the nineteenth century especially. We verified our determination of E
series for the nineteenth century by comparing the change of E with that of
G - 23
1800 1850 1900 1950
Figure 1. Changes of annual values of released seismic energy
(in 1018J) for 1800-197*0.
the annual number (N) of volcanic eruptions. The N data were taken from
Sapper (1927)- Figure 2 shows the variations of E (upper curve) and N (lower
curve) smoothed by 11-year sliding means. Figure 2 shows that the obtained
changes of both E and N are in agreement for the nineteenth century.
2. SPECTRAL ANALYSIS OF E AND OF RELATIVE SUNSP0T NUMBERS
Spectral analysis of both relative sunspot numbers (Rz) and planetary
seismic energy (E) was made by the maximum entropy method (Smylie et al.,
1973). Power spectra of Rz (upper) and E are shown in Figure 3 as a function
of period. The scale of the peak of the long-term component of E (with period
equal to about 1 80 years) is placed to the right of Figure 3- We shall not
discuss here either the origin of this component or the high-frequency com-
ponents of E (with periods shorter than 10 years). Our emphasis js on compo-
nents with periods of about 11 and 25 years in the E variations. These
periods correspond to solar and solar magnetic cycles. It is necessary also
to note that there are no long-term variations of E with a period of about 93
years, which take place in the changes of Rz.
It is interesting to make a comparison of the 11-year and 25-year varia-
tions of Rz and E, found by linear filtering of the initial series. For
convenience, we shall mark these components as E(ll), E(25), Rz(ll) and ^ (25) •
They are presented in Figures h and 5, which show that the connection between
E(ll) and Rz(ll) as well as between E (25) and Rz(25) is unstable.
G - 2k
1800 1850 1900 1950
Figure 2. Changes of annual values (E) of released seismic energy
(upper curve) and annual numbers (N) of volcanic eruptions. Both
E and N are smoothed by 11-year sliding means.
150 200
Figure 3« Power spectra of relative sunspot numbers R (upper curve) and of
released seismic energy E (lower curve). The scale of the peak of the long-
term variation of E is placed to the right.
G - 25
1850
1900
1950
Figure k. The 11-year variations of E (upper curve) and R (lower curve)
20 rE
0
-20
-lOr-Ri
L0
10
1850
1900
1950
Figure 5. The 25-year variation of E (upper curve) and R (lower curve)
G - 26
3. PREDICTION OF GLOBAL SEISMIC ACTIVITY OF THE EARTH
It is possible to make a statistical prediction of changes of released
seismic energy using the presence of the 11-year and 25-year E variations and
their connection with solar activity. We used the E data for the nineteenth
century only. The E data for the twentieth century were used for verification
of efficiency of the prediction technique. The prediction of E was made in
two ways.
1. Mean curves of E(ll) and E(25) were determined by a superposition
method according to the nineteenth century data. The years of maxima of 11-
year and 25-year cycles of R2 were taken as "zero years." Using the data on
the maxima of Rz(ll) and Rz(25) in the twentieth century the mean curves of
E(ll) and E(25) were superposed on the extrapolated curve of the 180-year
cycle of E. In Figure 6 the initial E (solid line) and the predictive E
(broken line) are shown. Both the initial and predictive E are smoothed by
3-year and 5-year sliding means and are presented as deviations from means.
The correlation coefficient between them is equal to +0.59. A marked differ-
ence between the initial and predictive E after 19^0 is probably due to the
unstable connection of the 11-year and 25-year variations of Rz and E.
2. Mean curves of E(ll) and E(25) were determined by the superposition
method using the E-data for the nineteenth century only. The Rz data were not
considered. The years of maxima of E(ll) and E(25) in the nineteenth century
were taken as "zero years." "Zero years" in the twentieth century were found
by extrapolation. The predictive values of E for the twentieth century were
obtained as in the previous case. Figure 7 shows the initial E (solid line)
and the predictive E (broken line). In this case the correlation coefficient
between the initial and predictive values of E is equal to +0.7^.
4°r»E
20
-20
Figure 6. The initial (solid line) and predictive (broken line) changes of
the released seisrr:~ ""^'^v, smoothed by 3~year and 5-year sliding means and
represented as deviations from means, according to method 1 (see text).
G - 27
-20 1-
Figure 7- The initial (solid line) and predictive (broken line) changes of
the released seismic energy, smoothed by 3-year and 5-year sliding means and
represented as deviations from means, according to method 2 (see text).
h. CONCLUSION
Spectral analysis of the E and R changes give evidence for the solar
dependence of the seismic activity variations having time scales in the range
of 11-25 years. On this basis the suggested prediction technique may be use-
ful for solving the prediction problem of the planetary released seismic
energy.
REFERENCES
Anderson, Don L. (197*0: Earthquakes and the rotation of the Earth. Science,
186:49.
Lomnitz, C. (197**): Global tectonics and earthquake risk. Elsevier Sci .
Publ. Co., Amst.-London-N.Y.
Earthquakes in the USSR (1963-197*0: Annual Reports, Acad. Sci. USSR. "Nauka"
Publ . Co., Moscow.
Richter, Ch. F. (1958): Elementary seismology. W. H. Freeman and Co., San
Franc i sco.
Sapper, K. (1927): Vulkankunde. Stuttgart, Germany.
Smylie, D. E., G. K. C. Clarke, and T. J. Ulrich (1973): Analysis of irreguf
larities in the Earth's rotation. Methods of Computational Physics, 13:391
G - 28
SOLAR TERRESTRIAL PREDICTION: ASPECTS FOR PREVENTIVE MEDICINE
Professor Eliyahu Stoupel,M.D.
Toor Institute of Cardiology, Beilinson Medical Center
Petah Tiqva, Israel.
A retrospective comparative study on total mortality and cardio-
vascular mortality was carried out among 3761 in-hospital deaths
recorded at Beilinson Medical Center, Petah Tiqva, Israel, and 536
cardiovascular deaths out of hospital, from 1974-1977. .The helio-
and geophysical conditions prevailing were charted, and seven factors
compared: monthly sumspots number (W) , average of geomagnetic
activity (K) , sudden geomagnetic disturbances (SD) , number of hours
with negative and positive ionization and deviation in the solar
gamma-wave propagation during the morning (fof^) and afternoon (fof2)
hours - (minimal and maximal) from the monthly median of solar gamma
wave propagation. The highest correlation between general and cardio-
vascular mortality with these seven factors was related to the sun
gamma wave propagation (fofj) in the early morning hours. During
the geomagnetic periactive and peristormy periods, there were signi-
ficant changes noted in the coagulation system, peripheral blood and
diastolic blood pressure. These data can be important in under-
standing the etiology of cardiovascular deaths which occur with
increased frequency during periods of increased geomagnetic activity,
and may be of practical value in projecting plans for preventive
therapy by advance interpretation of the cosmic data available.
This investigation is based on recognition of the factors cited below:
1. That the sun is the major "biological watch" regulator;
2. Recent advances in helio and geophysical monitoring systems, and the
availability of more sophisticated interpretation of medical and
physical data with advanced computer techniques (Gibson, E. G. , and
others) .
3. Increasing international scientific co-operation;
4. The premise that cyclic or periodic changes observed in human
physiology, epidemiology and pathology cannot be understood on the
basis of only anatomical and morphological phenomena (Tchijevsky,Ai. ,
1976, and others) .
The goals of this study were: a) to check the influence of some geo-
and heliophysical factors on general mortality and mortality from cardio-
vascular diseases in general and, in particular, from myocardial infarction
G - 29
(MI), cerebral vascular accident (CVA) and other cardiovascular diseases
occuring in and out of the hospital . b) to check the changes in coagulation
system and arterial blood pressure that are closely connected with the
mechanisms (pathogenesis) of a number of cardiovascular diseases. The study
was conducted in Beilinson Medical Center (B.M.C. - 1000 beds) and 5 neigh-
boring hospitals, from 1974-1977. The mortality data for the study of non-
hospitalized cardiovascular accidents was obtained in the Abu-Kabir Institute
for Forensic Medicine (Tel Aviv, 1974-1977, Vice Director Dr.B.Bloch). The
cosmic information was provided by scientific institutions in the U.S.A. and
the Academy of Science of the USSR.
MATERIALS AND METHODS
Daily and hourly index of hospital mortality in B.M.C. of 3761 hospital
deaths in 1974-1977, included: 818 cardiovascular deaths, 239 deaths from MI.
The cardiovascular deaths out of the hospital (determined by post-mortem
examination) included 536 cardiovascular deaths (among them 164 from MI, 27
from CVA, 43 from coronary arteriosclerosis without signs of MI or coronaro-
thrombosis, etc.). The study was performed on 1339 days, 683 non-active
(quiet or unsettled) and 656 periactive (one day before, the active or stormy
days and two days after them) . In addition changes in quiet, unsettled,
active stormy days, and particularly in pre-active- (1 day before) and post-
active (2 days after active) geomagnetic periods, were studied.
The activity gradation is demonstrated in Table 1.
GEOMAGNETIC ACTIVITY GRADATION - Table 1
STATE OF
QUIET
UN-
SETT-
LED
DISTURBED
FIELD
ACTIVE
MINOR STORM MAJOR STORM
K 0
1 2
3
4
5 6 7 8 9
AMPLITUDE
(gamma) 0-5
6
-10 11-20
21-40
41-70
71-120 121-200 201-300 331- 550
550
Arterial pressure of 550 healthy individuals was examined during
different geomagnetical conditions and 870 hypertensive patients who were
treated in the Hypertension Institute of B.M.C. (Dir .Prof . J.Rosenfeld) , were
also investigated. A study of peripheral blood and coagulation systems in
connection with prevailing geomagnetic conditions was carried out in co-
operation with Prof .H.Joshua (Clinical Laboratory Director of B.M.C). The
statistical analysis was performed in the Israel Institute for Productivity
(Dr. J. Levy) and the Computer Center of Tel Aviv University. In all results
the Student test was used (t,P.); in a part of results the null hypothesis
method has used for the daily mortality index- "x^" level (for analysis of
the influence of geomagnetic activity on mortality), correlation coefficient
(r) between various monthly heliophysical and geomagnetic parameters and
mortality, correlation between geomagnetic activity and number of basophyles
in the peripheral blood were investigated.
G - 30
Table 2 presents the correlation between total mortality, cardiovascular
and MI mortality and various mean monthly helio-and geophysical parameters:
K - geomagnetic activity index; W - sunspots number; S - sudden geomagnetic
disturbances; (+) ; (-) hours of positive or negative ionization, foF^ -
deviation from the median of SolarY wave propagation in the morning hours;
foF2 - this parameter in the afternoon hours. There is a prominent rise in
correlation coefficient between all parameters of mortality and foF^ (min) .
S is the number of monthly geomagnetic disturbances based on the deformation
of monthly cosmic data.
CORRELATION BETWEEN MONTHLY GEOPHYSICS PARAMETERS AND HOSPITAL MORTALITY
(JAN. 1974 - MARCH 1977) - Table 2
GEOPHYSIC
PARAM.
IONIZATION
W
MORTALITY
foFi
MIN.
foF2
MAX.
TOTAL
MORTALITY
BEILINSON
CENTER
2057*
76.18
11.3
0.27 0.043 0.312 0.008 -0.015 -0.583
0.245
TOTAL
MORTALITY
OTHER
HOSPITALS
1704
63.11
13.0
-0.166 -0.107 0.189 -0.292 -0.294 -0.431
-0.034
TOTAL
MORTALITY
(1+2)
3761
139.30
21.2
0.04 -0.043 0.282 -0.174 -0.189 -0.575
0.109
CARDIOVASCULAR
MORTALITY
BEILINSON
CENTER
818
30.3
10.7
0.026 0.029 0.228 -0.297 -0.318 -0.494
0.219
M.I.
MORTALITY
BEILINSON
CENTER
239
8.85
3.35
0.224 0.025 0.289 -0.050 -0.038 -0.271
0.162
* TOTAL NUMBER OF OBSERVATIONS
MEAN STANDARD DEVIATION.
G - 31
Six high and five low mortality months were chosen in B.M.C. and in five
other hospitals among 27 monthly mortality figures (1974-1977).
Table 3 presents the mortality figures for the 27 months analyzed, and
the Student test that confirms the statistically significant differences in .
high and low mortality during the months randomly chosen.
SELECTED MONTHLY HOSPITAL MORTALITY FIGURES Table 3
(Total and Cardiovascular) Jan. 1974 - March 1976.
CAUSE OF DEATH MAIN FIGURES
HOSPITAL NAME FOR 27 MONTHS
MAIN FIGURES
IN 6 HIGH-
MORTALITY
MONTHS
MAIN FIGURES
IN 5 LOW-
MORTALITY
MONTHS
DIFFERENCES
SIGNIFICANT
AT HIGH/LOW
MORTALITY
CARDIOVASCULAR 30.259±10.668
DISEASES/BEILINSON
44.666±4.633 16.600±3.209 P < 0.005
MYOCARDIAL 8.852±3.494
INFARCTION/BEILINSON
13.833±1.722
4.200±0.837
P < 0.005
TOTAL/BE I LINSON 76.185±11. 279
MEDICAL CENTER
91.50 ±2.81
61.000±2.738
P < 0.01
5 OTHER HOSPITALS 63. 111±13. 021
81.333±6.470
45.800±5.31
P < 0.005
Table 4 demonstrates the differences between various geomagnetic para-
meters in the high and low mortality months. The ± terms in tables 3 and 4
are standard deviations.
MONTHLY MAIN GEOMAGNETIC (G.M.) PARAMETERS IN HIGH AND LOW MORTALITY MONTHS
BEILINSON MEDICAL CENTER 1.1974 - III. 1976 Table 4
N
PARAMETER 6
HIGH MORTALITY
MONTHS
5 LOW MORTALITY
MONTHS
DIFFERENCES
SIGNIFICANT AT:
1
ACTIVE G.M. PERIODS
2.833
±0.408
2.000
±0.707
P< 0.025
2
LOW G.M. ACTIVITY
PERIODS
2.833
±0.408
3.000
±1.225
P> 0.05
3
HIGH G.M. ACTIVITY
GRADIENTS
1.167
±0.408
0.400
±0.5478
P< 0.02
4
EXTREMELY G.M.
PERIODS
5.667
±0.8165
4.000
±1.000
P< 0.02
Table 5 demonstrates the daily mortality indices and statistical
significance between daily mortality in and out of hospital in different
geomagnetic situations. In addition to Student test the differences in
hospital cardiovascular mortality were confirmed with x2 tests (x2> x2c)
For hospital cardiovascular mortality x2=12.449:x2c=11.070. For cerebro-
vascular accidents (CVA) -x2-11.60:xc2=10.597.
32
QUIET
0.94
ACTIVE
1.14
P
< 0.05
0.160
0.234
< 0.005
0.284
0.294
> 0.05
Table 5 BEILINSON MEDICAL CENTER
DAILY HOSPITAL MORTALITY INDEX IN DIFFERENT GEOMAGNETIC
CONDITIONS 1974-1977.
1. TOTAL CARDIOVASCULAR
DEATHS IN HOSPITAL (n=818)
2. C.V.A. DEATHS IN THE
HOSPITAL (n=269)
3. MYOCARDIAL INFARCTION
DEATHS IN HOSPITAL (n=239)
4. TOTAL SUDDEN CARDIOVASCULAR 0.367 0.373 > 0.05
DEATHS OUT OF HOSPITAL (n=27)
5. DEATHS FROM C.V.A. 0.120 0.273 < 0.01
OUT OF HOSPITAL (n=27)
6. DEATHS FROM MYOCARDIAL 0.096 0.161 < 0.02
INFARCTION OUT OF HOSPITAL
(n=164)
7. DEATHS FROM CORONARY ATHERO- 0.055 0.018 < 0.001
SCLEROSIS WITHOUT M.I. OR
CORONAROTHROMBOSIS. (n=43) .
OUT OF HOSPITAL
ELECTRICAL INSTABILITY?
Table 6 demonstrates the levels of systolic and diastolic arterial
pressure investigated in healthy individuals and in treated (drug controlled)
hypertensive patients - in different geomagnetic situations. We can see that
in the two groups the increased geomagnetic activity coincided with increased
diastolic pressure. The decrease in systolic pressure was significant only
in geomagnetic storms, together with a tendency to pulse pressure (systolic-
diastolic range) decreasing in active geomagnetic conditions.
33
ARTERIAL PRESSURE IN DIFFERENT GEOMAGNETIC CONDITIONS - Table 6
GEOMAGNETIC
IN
HEALTHY
IN
HYPERTENSIVE
ACTIVITY
PERSONS (1)
(TREATED) (2)
SYST.
DIAST.
SYST.
DIAST.
1 . QUIET
131.38
79.65
154.33
97.26
±15.67
±10.30
±24.33
±12.29
2 . UNSETTLED
132.62
82.49
154.42
97.33
±16.56
±10.80
±22.52
±11.90
3 . ACTIVE
131.01
83.01
157.26
100.64
±16.22
±7.76
±26.40
±12.88
4. PERIACTIVE
131.86
82.70
155.90
99.69
±16.40
± 9.67
±25.72
±12.62
5 . STORM
150.06
±15.58
98.83
±11.40
1^=550
n2=870
Tables 7 and 8 show the significant changes in various biochemical and
coagulation system parameters.
GEOMAGNETIC ACTIVITY AND SOME PARAMETERS OF HOMEOSTASIS - Table 7
INCREASE
1. NUMBER OF THROMBOCYTES
2 . PROTHROMBIN
3. PLATELETS AGGREGATION
4. FIBRINOLYTIC ACTIVITY
5. DIASTOLIC ARTERIAL PRESSURE
(PERIPHERAL RESISTANCE?)
6 . HEMATOCRIT
( IN COMPARISON TO THE
PERIACTIVE DAYS)
B. DECREASE
1. NUMBER OF BASOPHILES
(HEPARINOID PRODUCTION?)
2. TRIGLYCERIDES
( IN GENERAL POPULATION)
3. CHOLESTEROL
( IN GEOMAGNETIC STORM ONLY)
4. SYSTOLIC PRESSURE
( IN GEOMAGNETIC STORM ONLY)
G - 3k
SIGNIFICANT CHANGES IN THE COAGULATION SYSTEM CONNECTED
WITH GEOMAGNETIC ACTIVITY - Table 8
N
PARAMETERS
GEOMAGNETIC ACTIVITY
PROTHROMBIN
QUIET
PERIACTIVE
ACTIVE
STORMY
1.
75.7
78.5
79.9
79.9
INDEX (n*=1331)
± 7.10
± 7.45
± 8.16
±11.92
2.
THROMBOCYTES
177.055
195.025
182.110
205.064
(n=1053)
±90.047
±69.040
±85.840
±101.063
(POSTACTIVE-
213.056
±85.005)
190.448
±92.247
3.
BASOPHYLES
0.55
0.46
0.20
4.
(IN THE PERIPHERAL
BLOOD) (n=1934)
PLATELETS
± 0.27
33.7
UNSETTLED
34.0
± 0.21
40.0
± 0.26
47.0
AGGREGATION (n=162)
± 15.4
± 16.0
± 17.0
42
+
± 14.0
.0
16.0
*N - NUMBER OF TESTS
Table 9 demonstrates the parameters, that were proved, although without
statistically significant changes.
NONSIGNIFICANT CHANGES
Table 9
1.
ENGLOBULIN TIME
/
FIBRINOGEN
/
2.
BLOOD VISCOSITY
WITH TENDENCY
TO
3.
BLEEDING TIME
it
4.
CLOTTING TIME
it
5.
PULSE PRESSURE
WITH TENDENCY
TO
6.
TRIGLYCERIDES
( IN ATHEROSCLEROTIC
HEART DISEASE)
7.
GLUCOSE
8.
URIC ACID
WITH TENDENCY
TO
INCREASE
DECREASE
INCREASE
IN STORM
G - 35
The most significant changes were in increased platelets aggregation,
prothrombin index, thrombocytes count in the peripheral blood during in-
creased geomagnetic activity, together with a decreased number of basophyles
(anti-coagulant heparinoid productions); the fibrinolytic activity was
changed conversely with a tendency to increase.
The hourly distribution of 3761 cases of hospital mortality is
presented in Diagram 1.
MEAN
I 2 3 4 5 6 7 8 9 K> II 12 13 14 15 16 17 18 19 20 21 22 23 24
HOURS
There are two peaks in the 24-hour distribution: In the early morning
hours (5 a.m. -7a.m.) and in the afternoon (1-2 p.m.). The relatively
high correlation of monthly mortality index and sun wave propagation in the
morning hours was the course for selected analysis of hourly mortality in
the active and non-active days.
36
Diagram 2 demonstrates the two curves. There is a tendency to higher
mortality figures in the morning hours in active days. On the non-active
days the maximal hours were in the afternoon.
DIAGRAM 2
6.M. ACTIVE DAYS
NONACTIVE DAYS
n = 3732 DEATHS
8 9 K) II 12 13 14 15 16 17 18 19 20 21 22 23 24
HOURS
DISCUSSION
The influence of sun activity on a wide spectrum of biological
processes was confirmed in the investigations of M.Faure, A.Tchijevski,
G.Sardon, E.Budai et al. Tchijevsky wrote (1936) that human society will be
ready to discuss the problem only 50 years hence. Recently a number of
studies were performed to confirm the leading role of the central nervous
system and particularly the hypothalamus in interaction with magnetic waves
(M.Yiakovleva, C.Bamothy, I.Cholodov). Other studies confirm the importance
of the central nervous system in the regulation of blood pressure, heart
rhythm and coagulation factor (B.Lown, A.Myasnikov, J.Ganelina,
E.Rozhdestuenskaya et al . , I.Schwacabaya) . Those together can explain the
changes in coagulation factors (platelets aggregation and count, prothrombin
index), diastolic pressure increase in the active geomagnetic periods. The
fibrinolytic activity rose in general in active geomagnetic conditions (that
can be a compensatory factor for increased other coagulation factors pre-
venting thrombosis) and failed in patients with atherosclerotic heart and
peripheral vascular disease. Recent evidence points to the greater role of
thromboxan A2 - a product of platelets aggregation in the tonus of smooth
muscles of the small arteries (E.F.Ellis et al.). A higher level of
thromboxan A2 may be one of the factors affecting changes in micro-
G - 37
circulation in general and in the myocardium and brain in particular. This
together with the great influence of the hypothalamus on arterial pressure
in general can act as a stimulant to diastolic pressure increase and pre-
disposes to spasms of the coronary arteries (A.Maseri et al.). The influence
of geomagnetic activity on diastolic pressure was confirmed in the healthy
groups and the hypertensive patients in this study.
On the other hand the increase of sudden cardiac deaths out of the
hospital in the quiet geomagnetic days requires further investigation (the
group is only 43 persons) . That contradicts the point of view that the
complete isolation (A.Tchijevski et al.) of patients from geomagnetic
influence can be helpful for general prevention of cardiovascular accidents
connected with influence of cosmic factors. The absence of new myocardial
infarctions or thrombotic changes in the increased number of sudden deaths
from heart arteriosclerosis on quiet days is a factor which requires more
investigation if one suspects that quiet geomagnetic conditions may pre-
dispose to electrical heart instability (B.Lown, L.Meltzer) and sudden death
from arrythmias. Absence of any significant rise in hospital mortality
from myocardial infarction can be attributed to improved cardiac care in
intensive coronary care units in the last ten years. Previous investigations
conducted in 1968 and in 1971, showed increased hospital mortality
(I.Stupelis - E.Stoupel).
According to H.Jick, H.J.Weiss, Aspirin may play a useful role in
preventive therapy connected with coagulation changes in its effect on anti-
prostglandin activity (a group of prostglandins are precursors in blood
platelets aggregation) . This may have significance for regulating coagu-
lation changes during periods of increased geomagnetic activity. It also
explains the empiric tradition of the elderly population to use Aspirin for
all ailments connected with weather changes. The hourly dynamics of the
recorded deaths demonstrated the need for more care in the correct dosage of
drugs, to prevent insufficient concentration of cardiac drugs in the blood
and tissue in the early morning hours. The solar-terrestrial prediction
data can be utilized to great advantage for: 1) increased readiness in the
emergency medical services (ambulances, Intensive Coronary Care Units);
2) More efficient use of preventive therapy in high risk cardiovascular
patients, K.Novikova, 1968;Y.Jushenaite, 1969; Y.Ganelina, 1969; E.Stoupel
(I.Stupelis) 1970, 1976. The changes in hospital mortality (general and
connected with geomagnetic activity) from myocardial infarction, confirm the
progress in diminishing the number of sudden cardiac deaths occurring in
hospital over the last 15 years.
A bright spectrum of possibilities exists for more studies about
cosmic-biologic interaction for theoretical and practical biology and
medicine.
38
REFERENCES
Barnothy, J.M. (1964), in: Biological Effects of Magnetic Fields. New York,
1:93.
Budai, E. (1931): Taches solaires et meningite cerebrospinale. Revue de
Pathologie comparee et d' Hygiene Generale, 419.
Ellis, E.F., Oelr, 0., Jackson Roberts, L., Payne, N.A., Sweetman, B.J.,
Dates, J. A. (1976): Coronary arterial smooth muscle contraction by a
substance released from platelets. Evidence that it is Thromboxan A~.
Science 193:1135.
Faure, M. (1934-1935: Cosmobiologie. Nice.
Frishman, W.H., Weksler, B., Christodoulou, J. P., Swithen, C, Killipt, T.
(1974) : Reversal of abnormal platelet aggregability and change in exer-
cise tolerance in patients with angina pectoris following oral propanolol.
Circulation N. 4,50:887-896.
Frishman, W.H., Christodoulou, J. P., Weksler, B., Smithen, Ch., Killip, T.,
Scheidt, S. (1976): Aspirin therapy in angina pectoris: Effects on
platelet aggregation, exercise tolerance and ECG manifestation of ischemia
Am. J. Heart. 92, 1:3.
Gamelina, J. (1969): Sudden death in acute myocardial infarction and problems
of resuscitation. Klin. Med. 11:111-119 (Russian).
Gibson, E.G. (1973): The quiet sum. Scientific and Technical Information
Office. NASA, Washington, D.C.
Jick, H. , Elwood, P.C. (1976): Aspirin and myocardial infarction.
Am. Heart J. 91, 1:126.
Jushnaite, J. (1969): Solar activity and the pathology of circulation.
Sveikatos Apsauga. 5:3-5 (Lithuanian).
Kholodov, I. A. (1966): The influence of electromagnetic and magnetic fields
on the nervous system. IPRS-37102 (TT-66-33531) . Washington, Joint
Publication Research Service.
Lown, B., DeSilva, R.A., Lenson, R. (1978): Roles of psychologic stress and
autonomic nervous system changes in provocation of ventricular premature
complexes. Am. J. of Cardiology, 41, 6:979-958.
Maseri, A., Pesola, A., Marzilli, M. , Severi, S., Parodi, 0., L'Abbate, A.,
Ballestra, A.M., Biagiui, A. (1977): Coronary vasospasm in angina
pectoris. Lancet, Vol. 1, 8014:713-719.
39
Meltzer, L.E., Dunning, A.J. (1972): Textbook of coronary care. Philadelphia &
Amsterdam.
Myasnikov, A.L. (1954): Hypertonic disease. Megdiz Edition, Moscow.
Rozhdestvenskaya, E., Novikova, K. (1969): The influence of solar activity
on the blood fibrinolytic system. Med. Ref. Journal, 10:65-69.
Sardon, G., Faure, M. (1927): Les taches solaires et la pathologie humaine.
MLa Presse Medicale" N. 18, Paris.
Searman, G.V.F. (1976): Electrochemical features of platelet interactions.
Thromboses Res. 8(2) 235-246.
Schwacabaya, J.K. (1976): Actual problems of hypertensive crisis.
Kardiologya 5:5-11.
Stupelis, I. (Stoupel, E.). Jushenaite, J., Labananskas, J., Stahaityte, N.
(1970). The activity of the Earth's magnetic field, season, and risk of
death from myocardial infarction. Abstracts of the 7th Conference of
Internal Medicine, Latvia. Riga, pp 147-149 (Russian).
Stoupel, E. Forecasting in Cardiology. J. Wiley and Sons, New York, Toronto,
Jerusalem (1976) .
Tchijevsky, A.L.: Effect des facteurs physiques de la nature sur les elements
nerveux et sur l'activite nerveuse des animaux et de . 'homme rapport
presente au laboratoire practique de Zoo psychologie V. 1925 Moscow.
Traite de climatologie biologique et Medicinale V. 1:672, Paris.
Tchijevsky, A.L. (1976): Terrestrial Echo of the Solar Storms, Ilnd Ed.,
Mislj Ed. Moscow. Introduction, 0. Gazenko.
The Cosmic Data. Monthly of the Academy of Science of the USSR (1974-1977)
Weiss, H.J. (1976): Antiplatelet drugs - A new pharmacologic approach to the
prevention of thrombosis. Am. Heart J., Vol. 92, 1:86-102.
Wovikova, K., Gnevishev, N., Tokareva, N. et al.(1978): The solar activity
influence of the natural history of myocardial infarction. Cardiology
8, 4:109-112.
Yakovleva, M.I. (1973): Physiological mechanisms of effects of electromag-
netic fields. (Leningrad)
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